I tried searching but didn’t find anything recent so since this has been happening for a few weeks and I haven’t figured out the problem (done everything short of re-installing)…
ATC works and if I turn on the option to respond automatically to ATC I can usually make it through an IFR flight but the ATC window option in toolbar menu is “disabled” and scrolllock or any binding I setup to display the ATC window with messages and responses does not work. I am on the Beta program and think this may have started sometime around SU11 release, but not sure as I had been using ProAtc/SR but switched to trying default ATC.
If anyone has any ideas…I’ve looked at every option but can’t figure out what would disable the ATC window. Thank you.
Remove all Community Mods and restart the sim.
Thank you, I did try that (I’m using addons linker for everything in Community), so perhaps it’s something in the Official folder as I have lots of Marketplace content. I wasn’t sure what kind of add-on might disable this. I guess I can temp. remove all of the Marketplace content and process of elimination try to determine the offending addon. I thought maybe if someone has encountered this before there might be a clue where to look. 
I discovered the same issue this morning. I thought it might be the new Flow app from Parallel42 but since you removed everything from your Community folder, I guess that is not it. I’ll check AVSIM for anything.
I finally did find the solution to this problem a few weeks ago somewhere on avsim and nothing to do with any conflicting mods or addons. Basically I had to completely reset all of my settings to “default”, restart the sim then set back to “hard” or something like that. There were a few solutions I found in other forums doing a search. I’ll mark this as solution.
Thanks. I’ll give it a try. I don’t really ever use ATC so it’s not a priority for me right now. I found what I needed using the VFR Map (locating airport codes for private airfields).