PYDT doesn’t show any mods affecting saved games in the latest save.
This means the problem is definitely with you.
Try running a game file integrity check in the Steam client.
It’s possible some mod has left its mark on the database. That happened to me.
A file integrity check fixed the errors.
Thanks for the help, but unfortunately it did not work… 
I have posted on the pydt sites, but no response there yet.
In that case, we’ll ask matt_lambert to check the uploaded save. Or simply upload a new one.
I just noticed that I could download the turn again in the PYDT client, and did so, but still got the same message unfortunately. I did play a non-pydt multiplayer game just now, and it worked fine. No mods for that one. But at least I got my civ6 fix in this morning, other than the fix to the problem, haha. I did see that perhaps uninstalling and reinstalling Civ6 itself may help, so might try that after I have my weekend gaming session with my daughter.
Tried a couple things. Disabled all the mods, uninstalled and reinstalled Civ 6, removed all mods from my programs folder for Steam workshop (didn’t really understand it, but mods don’t show up now). Still not working, so I am at a loss. One issue on the internet is that the turn may have got corrupted somewhere, so perhaps going back in the turn if someone can redo it and reinitiate the process thus producing a new file?
OK, I downloaded the turn I played before this, and it loaded fine, so either we can restart for there, or have someone later in the current turn to try to do the same. Or I could just start it and we redo this turn if it works this way??? Let you guys decide before I do anything.
The host can Revert Turn. Then matt_lambert can upload new save. Hope this helps.
Thanks Alexander, but you may need to guide Steve on how to revert the turn. Sorry for this guys, not sure if it is a problem on my end, or the turn just got corrupted somehow. It has been a busy morning… got out of shopping with my wife though!!!
Okay. I don’t see those tabs on my version, that is there is no “Revert Turn” button for me right now. Do you see that button Blarney?
Yes I do, exactly as alexander depicts it. But I think since you are the host, only you can make it work?
Thanks, Oleksandr. But I don’t see those options (e.g. Revert Turn) on my page. See above screen shot.
Maybe those options come up on the turn of the current player??
Okay, my fault. I wasn’t logged in (but it looked like I was – duh). Anyway, relogged in, and Reverted Turn back to Egypt.
Hi all: WE ARE BACK!!! Sorry for this, but glad we got it worked out. I spent quite a while yesterday trying to figure out the problem, but learned a few things, and definitely got better at navigating discord looking for help on the issue… 
Hopefully doesn’t happen again.
No problem. Thanks for figuring it out. Well, if it happens again, at least we have your notes on how to fix it.
Hi all: and mainly the vets Alex and Matt. Got a question about additional rules that are expected in multiplayer. I see there are optional rules listed on the PYDT site and some exploits that should be shunned. It also says that if there are no rules posted by the host, then there are no rules. I assume that means anything goes in our game, right? However, from your experience, what is the general attitude to these types of rules, and what are the standard ones. I did notice on the CPL site, that their rules are VERY defined, and I don’t think that is what is happening in these non-league games. Can you guys just give me, and likely Steve, a sense of this? Thanks.
As you say, I’m treating this game as FFA which means there are no rules. I don’t fully understand the exploits which people might take advantage of; I just play to have fun and things like that don’t seem like fun to me. CPL rules seem too much to get my head round which is why I don’t tend to join CPL games.