Hi.
 
Down in the device manager for usb ports...did you go into the Preferences of USB ports and deselect "Let windows turn off this Port"...?
 
Part of power management tweaking , is said to stop this sort of off and on...issue.
 
Windows waits for ports to be engaged with a Plug into usb, then it sorts the driver.
 
if always on..and always connected...when you turn on your device MPK49...if booted into windows, should engage the usb port...and not go off at all, if that selection is set to not allow win to turn off.
 
If booting up OS with MPK49 on...It should be detected...also .?
 
So check that...Windows might be set to turn off your usb ports, to save power, if it believes it is not in use.
 
Now this awareness of the OS and usb ports/devices...is not perfect...
 
Some devices seemingly need to be (worked around)..and some work when turned on before boot, and some might need to be turned on after boot up of the OS and all services and drivers loaded.
 
Perhaps something liken is with you?
 
Just thinking out loud.
 
Cheers.
 
 
 

phil5633
I just completed a new DAW build

Based on this point, you really shouldn't be experiencing a shortage of Windows midi ports on a fresh build.
 
I agree with Les on this one, and the answer probably lies in Windows recognizing that the controller is active and has started the driver when you need it.
 
In my opinion the "Class Compliant" USB device drivers built into Windows are mostly hassle free, making any device that can use them truly plug and play. I don't know the specifics of the MPK49, but I used to have a MPK Mini that used class compliant drivers (no driver files to install, truly plug and play).
 
The only notes I saw from Akai on this unit is this: 
 
"Make sure that the MPK49 and all external devices are connected and that the USB
cable is connected to your computer before opening any software applications on your
computer with which you might want to use the MPK49. If the unit is not plugged in
before, your software application might not recognize the MPK49 as an available
device."
 
You would probably have better luck dealing directly with Akai support, than asking general Windows users about MIDI.  The Microsoft answers forum moderators might as well be bots, from what I have seen.  The level of expertise at TenForums https://www.tenforums.com/ is a bit better, but you are probably pushing the edge with a niche midi question.

I don't mean to hijack this thread but I am having the same problem with my Alesis Q49 USB midi controller.  It was working just days ago and now not. It shows up in device manager, it seems to be sending midi messages to windows but Cakewalk does not seem to respond to them.
I did notice that it says the drivers were "migrated" on 6/17/2017?  Was this a Windows 10 update?

Midi OX won't even open my USB Keyboard input. It says "Out of memory"
 

reginaldStjohn
Midi OX won't even open my USB Keyboard input. It says "Out of memory"
 

If you cannot open your keyboard driver in MIDI-OX, then you most likely have Windows issues ...
 
http://www.alesis.com/classcompliant
 

What does "class compliant" mean?

---

A class compliant device is one that does not require an extra driver from Alesis to connect to your *Windows computer, Macintosh computer, or iOS device. A class compliant device uses drivers that are written by Microsoft or Apple, and come pre-installed on the computer.
*Windows (98SE and up) is required for class compliant support.

I would agree with that except that if I open a synth in stand alone mode, like UVI then I can play it just fine with my keyboard.  Even in Sonar I can see the keys being pressed in the PVR but no sound comes out. I have toggled Midi Echo and that doesn't help.
 
Maybe I will try a different project.

OK. then start your own thread, post your details, and see what suggestions you get that can help to to solve your issue.  Piggybacking on another post is confusing for all involved, and will not speed up your problem solving.  There are many differences in system configuration, devices, etc., that can sound similar to yours, but it is always best to begin from a baseline with your specific config.

reginaldStjohn
I would agree with that except that if I open a synth in stand alone mode, like UVI then I can play it just fine with my keyboard.  Even in Sonar I can see the keys being pressed in the PVR but no sound comes out. I have toggled Midi Echo and that doesn't help.
 
Maybe I will try a different project.

Did you ever get to the bottom of this as I've been having exactly the same issue with USB midi. Keyboard works on a synth outside Sonar, not inside. Works using an old school midi din into my digital desk which then comes in over firewire