If possible :
- Test in a new project with settings back to default and making routing from scratch like you are used to.
- Test with another cable?
- Test with another Mic or source?
- test with another interface ?
This way you can target where the issue might come from.
Of course at first you want to check your gain / mute settings, be sure you enabled phaton power if needed for your mic etc...
Its often a little thing like this ^^
Hope this might give you some leads,