Lost access to folders in time machine backup

I had my old macbook backed up on time machine. I gio a new macbook air recently and installed everything from the time machine backup.

Just now I connected the new macbook to time machine to back it up. Time machine asked me if the old backups sould be claimed by the new machine and I ageed, as the old machine does not exist anymore. Unfortunately I have now lost permission to access the folders on time machine which belonged to the old machine (music, movies, documents etc.)

What can I do?