Seems that the issue might just have been with the PermissionsManager plugin (the permissions for OfflineRaidProtection do not appear there (between N and P, cuz it sorts plugins alphabetically)), i was able to find the permissions for OfflineRaidProtection via carbon panel (/cpanel)
Apologies for the troubles, it works now, it was all my fault.
What probably messed me up is what i did:
1. installed the plugin and didn't find permissions for it on PermissionsManager
2. Tried /raidprot command, which didn't give me any "no permission" error
3. Tried to give "offlineraidprotection.admin" to myself using c.grant manually and then tried /raidprot again, which didn't give me any output again
4. So i assumed that it must be a plugin issue, while it was my fault, didn't knew that /raidprot only works when offlineraidprotection.protect is granted
For anyone else who might run into similar issue, try granting the permissions to player groups manually using o.grant/c.grant
Or for carbon users, use /cpanel and then you can find permissions for it there