This just started happening the last couple days working on a mixing project.  20+ tracks, lots of plugs on everything, etc.
I stopped playback to load another plugin (Neutron Exciter) and went to play back.  No sound at all, but all meters show signal.  No routing changes or volume changes in the new plug.  Even if it's on a buss/aux that doesn't carry every signal (like vocal buss), no audio.  Sometimes I can undo and will get sound back.  Sometimes I can disable and enable again the audio engine and get sound back, but usually not.  However, if I close the project and reopen it, I have sound.  Even after I load the plug and keep it (with no sound), I can restart the project and will have sound.
 
No clicks or pops, no audio engine dropout.  CPU is at 25-30% tops.  It's not just izotope plugs, also happened with adaptive limiter.  No crashes either.  
 
Oh, it also happened after I froze about 8 tracks.
Also happened after bouncing the whole mix to a track, and soloing to the master buss.
 
Doesn't seem to be related to specific plugs, doesn't seem to be routing, doesn't seem to be CPU issue.  I'm thinking audio driver?  VS700, i know I won't get any support for that.  Just brainstorming...
I'm stumped, any ideas?  
thanks,
Dave

Isn't this a new machine? Have you tried the recommendations supplied by the dropout toast message like this one from troubleshoot section in the documentation? There are AUD.ini variables to mess with too such as DropoutMsec.

Yes new comp. I forgot to mention my driver sample size is 1024 for mixing.  
That is a great link, I have not messed with playback buffer sizes (ever), and have never heard of this AUD.ini  
 
I'll try those out, thank you Scook.
dave

AUD.ini variable documentation

So, I've been through those settings for a while.  I'm not sure it's helping, I'm still getting same audio dropouts.  Changed the dropout setting to twice the sample buffer (currently 1024), changed plugin buffer to 64, I'm not really sure if it's doing anything at all.  It's not even consistent now...which I guess is good so I can get my work done haha.
 
I thought it might just be Izotope plugs, but also happened when I loaded LB MB.

I've seen this same symptom a couple of times, not often or reproducible enough to report, but enough to mention here. Similar situation to Dave's, and it was with an iZotope
 
I have also hesitated to report bugs and crashes and such so far because CbBL is such a feature-rich DAW compared to the one I am used to and I am so new to it, but man, the audio engine sure does shut down a lot. I'm used to Mixcraft where it happens about....hardly ever.
 
I will study that documentation on the AUD.ini file.

Update, I thought at first this was due to the size of the project, but twice this has happened with a blank project template, no Izotope, and simply importing an mp3 into an empty track.  Press play and no sound.  Close project, reopen and everything works.
 
Also, I submitted a ticket to Bandlab, and detailed my system.  They suggested I switch from ASIO to WASPI.  I'm not even sure that's possible with the VS700 system?  I won't get a chance to try until probably tomorrow night, curious what you all think of that recommendation.  I've never used WASPI or MME.
 
Dave

Another update, nothing has worked.  One thing I did try was a Scarlett Solo usb interface I have for home.  Added the driver and everything worked very well.  So, that sucks.  If it is the VS700 and/or the driver, I'm screwed.

I may be way off track here guys but at this stage Im sure you'd listen to any suggestions as these dropouts are infuriating.  You see i was also getting these a lot.  Im using an M Audio device which is USB.
You know what fixed the dropouts for me?
Dont laugh..I deadly serious.   I went into device manager.  Went into the properties of the USB ports......and disabled the power saving.    No more dropouts.    I know it's weird suggestion bro but hey just throwin' it out there. 
Hey you never know.  it just might work.  

I'm sure you have done this since you sound pretty thorough, but I had problems with Malwarebytes, my virus program.  When I turned it off to use my daw, the problem was solved.  Pretty much anything tuned into the internet tend to mess with my daw, so I run it totally clean now with nothing on.  I was having the same issues you have.