I have disabled my VPN, and did everything in a private browsing window, but every time I get an email verification link, it immediately sends me to a page with a 403 error. Does it need to be this difficult to create an account?
“Invalid signature” suggests to me that either the link expired, or something is mangling the link that we send to you meaning you’re opening a different link.
Every time I have requested a verification link, I have clicked it within just a few seconds, so it should not be expired. All I did was click the link in the e-mail (in Gmail), so I don’t know what could be “mangling” the link. I especially don’t know how to successfully verify my email address beyond the steps I have tried taking.
Some email providers do not open the link directly but instead open it with some “privacy link” thing that sometimes will strip tracking parameters from the URL. I know iCloud do this, maybe gmail have something similar in it.
Since sign up links contains gibberish it’s entirely possible that it gets classified as a tracking parameter and gets stripped.
The solution (given that this is indeed the case) is simple. Don’t click on the link. Instead copy the entire link yourself and paste it into a browser tab.