I have sonar 5 producer and I have a tascam us-1800 audio interface. Sonar shows the drivers for all inputs and outputs,and i have chosen which to us,but when I play something I get no signal.Am I missing something. I have been using cakewalk products for number of years now,but not with an audio interface before. Just with a mixer through the sound card.I have never had this problem. I got an interface because its all I`ve heard is that its the way to go.Especially if you want to record drum sets and stuff that needs a lot of mics. I know I probably am just missing some stupid little step,but can`t figure that out. Help me please.

Sonar 5 is pretty old but I guess it might be the same as what I'm used to. 
First things are , are you using an old Xp 32 bit computer or a Windows 7 64 bit? 
 Reason being I have the same interface more or less and it never worked very well with Xp 32 bit. But it works fine now with W7 64 bit as the drivers are more stable. 
 
Sounds like you have the drivers installed and they are showing on the driver list/ 
 
Plug a mike into input one. Turn up the gain until the peak light shows action, this will be just past 12 o clock for most dynamic mikes. 
 
Now in Sonar go to the input list for the track your going to record and chose 
Left us-1800 mike 1. You should now see the level meter moving when you talk. 
Arm the track for record. 
An oddity of the input list is input 2 will show as Right us-1800 Mike 1
 
 

Yeah I am using old Xp. I have done all that other stuff and still nothing. Just doesn`t make any sense. Grrrrrrr

Are you getting no signal, or just not hearing anything? IOW, if you hit Record, does something end up on the track? If so, maybe you're just not hearing the signal because Input Echo isn't enabled. However, if you are truly getting no signal despite having selected a valid input channel, then a) you're not plugged in to the interface channel you think you are, or b) the interface channel's gain control is turned down or off. I am not familiar with the Tascam interface so this may not apply, but some interfaces have separate mute and volume controls for each channel.

 Your not being clear about what is not happening. 
Not getting a signal would mean no INPUT. No sound in the headphones, no peak light action, track level meter does not move. Which channel are you using? A mike or are you using 9/10 instrument inputs? 
 
No sound is like Dave is saying, no OUTPUT which required different trouble shooting. 
 
Here's some OUTPUT stuff. 
My guess is your Master bus is set to Digital ( SPDIF) output. This happens to me when I load old projects that where made using an other interface. 
 
The US 1800 has 1/2 - 3/4 and a Monitor output. 
Use the monitor output for your studio monitors so as to utilize the control on the front. 
This control does not effect the headphone jack so it's easy to shut down room monitoring when tracking with a mike. 
And I would imagine you figured out the blend control too. This allows you to mix the input signal with the computers playback.
You'll find yourself using the 3 monitoring controls all the time. 
I run 1/2 and 3/4 into my Mixer for additional monitoring options. 
 
Don't use input echo with a Tascam while tracking audio as there will be around 12 ms or more delay from the Round trip latency, use the direct monitoring using the controls described above. When you upgrade to a newer system the RTL will drop to 6 or 7 ms but for me even that is to much while tracking. 
 

Check the Windows mixer and the mixer for the US-1800 control panel utility. One of those may be turned down or muted. 

Yeah its an input problem.Peak light is not showing in Sonar. Peak comes on in interface just fine. And both mixers are fine.

So 3 days have passed and you have not resolved this???
 
Your not giving us much information and if you did do all the things recommended then you should not have a problem unless the Tascam is malfunctioning. 
 
Are you absolutely sure you understand the track input list? 
 
You need to select the correct input from a drop down list that will in your case have 24 things to select from. It's confusing as the even numbered inputs show as odd numbers but as the right side of a stereo pair. 
 
Hey Dave- The Tascam does not have a GUI mixer. And because he said he sees all the Tascam in/out's in Sonar ,( audio options drivers? ) I assumed the Tascam was recognized by Sonar but that does bring up the point if they are grayed out and his on board is still not. 

Sorry it takes me so long to get back. My job schedule messes me up. So the 3 days that went by I wasn`t able to try anything.What other info could I give you cactus music to help me along?

URIELSUITE
Yeah its an input problem.Peak light is not showing in Sonar. Peak comes on in interface just fine. And both mixers are fine.

OK. So the signal is getting into the Tascam, but not making it to the computer. 
I'm assuming you have an electric guitar plugged into either Input 9 or 10 on the front panel and you have the corresponding Guite/Line In button pushed in. Adjust the gain halfway to start. (Put some headphones in the US1800 and make sure you hear the guitar.)
In Sonar, Options-Audio-Drivers you should have the US1800 selected for both Input and Output devices. 
In Options-Audio-Advanced, you should have ASIO selected as the driver mode
You should have an AUDIO track selected with the Input set to the US1800
Arm the track (Press the R button)
Turn Input Echo on. (the button next to M S R)
Press record and start playing anything and see what you get.