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Repair Outer Defenses is NOT listed as a City Project
Ancient Walls are damaged
Medieval Walls are thus unable to be built
and Temple of Literature is unable to be built
both require Ancient Walls
normally, Ancient Walls [damaged] in Renaissance era would trigger the Repair Outer Defenses Project as a visible project in the list of projects.
it was not listed in Production Panel {v1, v2, single city panel, single city queue, multi-city queue, toggling any of these did not help matters]

I will try to recreate the error at some point with CUI only. I don't know how to recreate the error.

I don't know how to damage the walls sufficiently to trigger the condition to test it in the "sterile conditions" that you wish things to be tested in.

I suppose I could nuke my own city lol

@sdgabai - IIRC you can destroy your walls with Cheat Menu Panel:

https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=1528155583

but I have no idea if that's going to be useful or not.

BTW it looks like you take this mod managing as a job :)

lol, you might say i have a bit of an electronic age addiction :D [mostly computer games, but, it also includes social media, TV, and other stuff too] I do most of our financial stuff, costumer service calling when we got problems and tech support calling, etc. Bob does IT for a living, so he doesn't need the stress of it a home. I'm the math nerd of the family.

Your city needs to wait 3 turns after being attacked before the repair can start.
That is a game mechanic.
I've tested it, works the same on vanilla, ppv1 and ppv2.

In the course of prepping to nuke my city lol
I did show that the Recommission Nuclear Power Plant may or may not be bugged at age 0.
I'll have to test later ages.
It doesn't display the age the first time in v2, until you toggle v1/v2 a couple of times.
It is no big deal, if you remember to toggle v1/v2 a bit.

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i'm going to test the multi-player session where it happened, with EVERYTHING disabled. i think it may be a vanilla error?

https://civilization.fandom.com/wiki/Repair_Outer_Defenses_(Civ6)

I'm just posting the Wikia entry for future reference, in case someone Googles this page.

Thank you, guys, for your patience. In many ways, there is a ton that I don't know about this game, and will probably never know [or will take a very long time to learn the rest)

No problem lady.

Cannot place districts with Concise production panel mod enabled. I enabled this mod in an existing game, with Production Queue mod enabled. I DISABLED that mod and loaded back in and it still wont work. Am I not able to use the Production mod on this save because of that mod? I even unsubbed from it. I did start a new game with Concise UI mods and it worked fine. Is there a work around to get it to work on current game? or am I screwed...

That's an old bug with Production Queue. Some mods linger on saves even after removed, and I do not know a way to solve that.

Try a new game and see if everything works.