I've been going back to mines that I've mined before and it showing them respawned but I can't click on them to mine them. Is this a known bug and is there a fix for it?

I'm on Xbox 360 with Dawnguard. If that matters...

The respawn time for mines are 30 ingame days. Important to not visit those places again, because it resets the respawn time.

And just because it visually seems that they respawned it doesn't mean that you can actually mine them. You know: one month.

Since the ore veins will take 30 days to respawn, avoid the mine for 31.
Then...
- Enter the mine
- EXIT the mine
- Enter the mine and harvest the ore.

I know it sounds silly, but this has worked since the game's release. Waiting 30 days is required for the cell to be able to reset. Waiting 31 is just insurance so you don't have to start over. Entering the mine will show color in the veins, though mining is not available. Simply exit the mine and re-enter and you'll be able to mine. Goofy as it sounds, it most definitely works.
Hope that helps

Edit: I have both PC and Xbox360. This works on both.