Check this post, I had issues with the contents of the .smbcredentials file. The usernames must be really simple, (notably excluding spaces), although it looks like you might have already done this.
AutoFS issues after Bullseye upgrade - #6 by thechrisgregory
I had a look at your logs, but couldn’t see the ‘[osmc mount]’ messages. Can I suggest you re-up the logs, capturing startup, when you expect the mounts to be started.