Can't drop transitions - previous transitions disappeared

Hello! I am fairly new to DV. I upgraded to the latest version. A few days ago I couldn't drop a transition between clips, that both have plenty of tail on each. I spent a long time trying to figure out why they wouldn't drop. I don't know what I did, but suddenly they worked again and showed up as the usual white transparent box between clips. Today, all my transitions are no longer visible and I can't drop transitions again! When I pull one over it's just greyed out. Help!!

Have you had a chance to complete any training for Resolve yet, Michelle?

https://www.blackmagicdesign.com/produc ... ning#books

Yes, I took a course on Resolve but that didn't answer my question.

The issue is at least temporarily resolved. I opened a new project and pulled some clips in and the transitions worked perfectly and as expected. I returned to the project I was working on and they were once again working. I don't know whether this just a software glitch or what but closing and restarting Resolve didn't solve the issue, the only thing that worked for some reason was switching projects.

Hi, figured out similar problem with adding transition. Couldnt add them on trimmed clips and audio, tried everthing and finally - in preferences ->user -> transition duration - change to frames or change the duration
Anyway I didn't face the problem with dissapearing effects. Hope it helps.