Just wanted to add that this is probably related to
As I’ve stated below:
You just have to make sure that you don’t(!) enter the password when Mountain Duck asks you to do so. Because once you’ve entered the password in Mountain Duck, Cryptomator can’t access the encrypted data anymore because they’re already decrypted by Mountain Duck.
If you think that it’s a different issue, please check out the log file if there are any error messages.