I DLed NVSE today from the silverlock site but whenever I run New Vegas from steam I always get a message saying that I need to update New Vegas, but it is fully updated I made sure. I've reinstalled NVSE twice but it still isn't working, any ideas on how to fix it?

Be sure "Enable Steam Community In-Game" is checked for NVSE to run properly. Also you may have downloaded the wrong version of nvse. You could try running the game by opening the nvse loader first.

If it's telling you that you need to update New Vegas, that's what you need to do. The current latest version is 1.2.0.352; you can check which version you have by right-clicking on FalloutNV.exe, going to the Properties window, then the Version/Details tab. The loader .log files also report this information.

Steam won't update to the latest version for some reason, any ideas?

what version of NVSE are you using? 1.7 or 1.8?

1.7

You might be getting that message because you should be using NVSE 1.8

Do a search in this forum for NVSE, in the official thread there will be a link to download 1.8

I don't know why they haven't put a link to download 1.8 on the silverlock website, it's causing a LOT of confusion,
considering that a 1.9 is going to be coming out after the patch.