My game is overflowing with mods and it may be one of them that is causing the problem. I have reached the part where you shout the mists away and battle with Alduin with the Nord heroes. I have used the Dragonrend shout and it takes a few shouts before he finally lands. After the first landing he seems to have about 10% health gone (although I believe that the Nord heroes are the ones that damaged him). After this point he will not take any damage even after landing a few times with everyone hitting him with their weapons repeatedly(this was done for about 45 minutes).

Things that I have tried so far:

-Restarting at a save as I entered the Hall of Valor where I found the Nord heroes (resulting in the same outcome)

-Setting Deadly Dragons(mod) to vanilla difficulty

-Disabled combat AI via console commands (This is how I discovered that I couldn't do damage to Alduin, and also I could do damage to my follower)

I have searched for the problem but I have only found solutions for the first battle with Alduin which seems to have a similar bug. If anyone has an answer or suggestion as to what I could do I would gladly try their solution.