Try deleting (forget) the network on your device and then re-add it.

I would go with a pure mesh router system over using an extender and router combo. That is what I plan to do when I replace my current router. I also have an extender to cover a dead spot in my...

I do not understand why either. You may want to try the EN forum as this is the US one. They may have encountered the issue since they see the EU version a whole lot more....

Check the label on the router and see if it has a country code as your router may not have been a EU model. This may help https://www.tp-link.com/us/choose-your-location/

Sounds great. Have you done any recovery using the BackupBundle?

It is your Windows 10 that does not have SMB2. Google SMB2 for more info.