Playback issue making AE unusable

[spomeniks]

Hey everyone, I'm having a serious problem with AE currently and could use any advice.

All of last week I'd been working on a project. On Friday, halfway through the day my composition just stopped playing back - either by scrubbing through the timeline or hitting spacebar. I had not introduced any new types of effects or layers when it happened (most of the project is just text layers). When I go to quit, I always have to force quit for that to happen. I load the project back up, can do one spacebar preview, hit spacebar again, and from then hitting spacebar or scrubbing through different points of the timeline does nothing (no preview, live or RAM, timeline indicator - aka the blue line - does not move automatically). The app is fully functional - keyframes update as I move through the timeline with the mouse, and I can use all menus, but nothing else.

This is the only other instance I've been able to find. Weirdly enough, I use a Thunderbolt monitor externally and simply unplugging it helped on Friday for a few minutes. Aside from that, my audio settings are all system default, and having no external monitor plugged in, no headphones etc. makes no difference

So far I have tried:

Migrating previous settings

Re-installing AE

Changing the drive for cache to an external SSD, and cache size (from 36gb to 100gb)

Using a different user account

And nothing has made a difference

System:

Late 2017 iMac 27", Catalina 10.15.4

i7-7700k

20gb DDR4 2400mhz

Radeon Pro 580 8gb

500gb SSD (whole project has been on an external drive)

I'd really appreciate any advice on this, let me know if anything else would be helpful. I should add that I've only been using AE for a few weeks, but have done some smaller projects previously with no issues.

EDIT: I forgot to add that even if it is associated with the audio output issue, the composition I'm working in has no audio layers

[spomeniks · Accepted solution]

After an hour long phone conversation with Adobe support, I wanted to update this in case anyone else has the same issue.

In my composition are a couple of animated icons that I'd gotten from Motion Array. It turns out that they have issues in their expressions that seem to have been causing the whole issue. I hadn't suspected them because they were the first layers into the project and were working fine for 4 days. Because he didn't write them, the support guy's answer was basically "scripts be crazy". Started a new comp without the layers with expressions being copied over, and everything seems to be fine now.

[Kate Oram]

please try: 

after effects > preferences > video preview > enable murcury transmit and click adobe DV

[Kate Oram]

for the people that still have a problem with things not working with the real time previews