All good suggestions above.
Make sure that the pin on your mod's 510 is not somehow depressed or stuck, sometimes stuff can get in there and cause issues. Swab it with a q-tip soaked in rubbing alcohol.
If your tank does not look like it may faint at the notion (some tanks just don't like this I would reserve it for last and only if you know the tank and pin are otherwise goof) you may be able to screw the internal screw in the mod a few turns gently and see if that extends it enough to read. I cannot emphasize enough how much to do this last.
Get a spacer which may (in theory, I have not PERSONALLY had a ton of luck with this method) or heat sink which will serve as a "bridge" between your two connections, hence resolving the connection issues. Yeah, like I already said, this won't always work but sometimes it will.
Good luck try not to panic.
Anna