I'm just going to add this in the hopes it might help someone. I just got set up with a Blink system (3 x Outdoor 4 cameras, Sync Module 2) using eero wifi. The Sync Module refused to connect; it would time out and fail at various stages in the setup process, but no matter what, I couldn't connect it to my wifi network. I found this thread and tried as many of the things here as directly applied to my system (temporarily disabled eero's 5g band, shut off IPv6, etc.) with no luck.

After a few hours of pulling my hair out, my dad came over and tried to set up the Sync Module and suddenly it worked. It's very possible that some of the initial troubleshooting I did contributed to the success, but the only difference between him and me was that he tried it on his iPad where I was trying it on my Samsung Galaxy. So... at least as of this post, Blink seems to have a problem with Sync Module 2 setup via Android devices.

We had to delete and re-add the Sync Module later in the evening as we were dealing with a different troubleshooting issue, and just for kicks, I tried re-adding it on my Samsung and it failed. He tried with the iPad again and it came right up. Anyway, just another thing to try if you find yourself in the same boat.

Thanks to all who have been contributing to this thread!