Modpack version
1.64d

Can the issue be reproduced?
Yes

Issue
I updated the modpack from version 1.63 to 1.64d and now I can't access anything in-game without being an OP. No one is OP and no one can access anything. We didn't change anything besides update the pack. If I OP myself it works but I don't want anyone to be OP.

well I fixed the issue. It was spawn protection. I set the spawn protection to 0 in the server.properties. Weird how it was the default value before and it was working fine.