Ok, went back through the thread a ways and did not see an answer. I just got around to playing FC5 again so I purchased the Season Pass and downloaded the DLC's. I followed the usual instructions firing up the latest trainer version, turning Steam and Uplay in offline mode, turned off the Internet and fired up the game. The game boots up fine using F2, F1 starts the trainer and everything looks good. The moment I click on one of the DLC's, Lost on Mars, etc., the game tells me I cannot play them with Uplay in offline mode. Fix?
[Edited by DGrant2561, 8/12/2018 7:24:44 PM]
I believe you must star the game normally with no trainer once after each patch/DLC install, so Ubisoft servers can verify your content.