A couple people reported the same earlier, seems to be a failure of the server client to download the latest updated version of the mod; you end up with a definition mismatch between player and server.
Deleting the file for the mod on the server and either forcing it to redownload or manually uploading the mod file from your own machine should fix it

i personally think there is / was a steam update problem, the update of Space engineers war done yesterday on my computer and lasted for ever. The primary update of industrial overhaul 1.2 was fast but the hotfix wont load until i went to the mod-selection screen of the game simply doing nothing but pressing ok. May be a coincidence but after that it loaded the hotfix and everything was fine. That was well over an hour after you uploaded the hotfix.

My save doesn't have a chemical plant. There is a chemical refinery but it doesn't accept lithium or niter ores.

We had the same issue, clients had the new version but the dedicated server did not. We manually copied the mod folder from the client (definitely v1.2) onto the server and everything started working fine