Yes, sometimes when I place lots from the Gallery I can't select them for events. The venue type doesn't update properly—it appears to be one type but it is actually set to something else. I don't know what causes it or whether it's mod-related.
If you use any mods, try testing without them in a backup version of your save, then in a fresh save.
You could also try changing the venue type to another venue, going to Manage Worlds, going back into build mode and changing the venue type back to the original/intended venue type, and then loading back into your household and trying again to select the venue for your social event. This is what usually works for me.
Also, some venue types are not enabled for certain events. In the vanilla game, restaurants are not available for engagement dinners. I'm unsure off the top of my head if they will work for other wedding events. But wedding venues should work, I think.
I hadn't tried changing the venue type going back out and changing it again so I will try that with the wedding venue for the actual wedding. I ended up just having the engagement party at another lot. I don't use any mods at all. Thank you for your reply, I can't believe I didn't think to try changing the venue and back again.
