Cannot access to drive
I launch cryptpad docker conatiner
docker run -d -p 3000:3000 -p 3001:3001 promasu/cryptpad
main page is fine:

However, after register, http://192.168.0.2:3000/drive/#

Did you already take a look at the /checkup/ page if it prints out any errors and does your browser console show any errors?
I have similar issue after updating to 4.12.1 (4.11.0 before). It seems the node process inside docker listens on 3000 port only, but not 3001. I haven't found anything useful in logs, but the /checkup/ page list various errors related to sandbox domain connection error (not surprisingly).
I have this issue as well after pulling the latest image, not being able to access the drive.
I thought that I'd just roll back to 4.11, but I have reason to believe that on docker hub (promasu/cryptpad), a lot (or all?) of the older images are on cryptpad version 4.12.1 regardless of the image tag. I pulled image versions 4.11, 4.10, 4.7. They all have version 4.12.1 of cryptpad (I checked that the docker container was using the correct image). Many of the images with on docker hub have identical digest across versions.
I was able to roll back though by cloning this repo (and subrepo) and build the image myself to roll back to 4.11.0.
Looks like my buildserver is doing some nonsense. I'm really sorry about it. Will look into the issues on appx on Sunday