Can't Login to Piwik: Form security failed

I have just migrated Matomo to Cloudways and am having the same problem.
It is now in a subdirectory of a domain with WordPress, if that matters…
Piwik worked for me flawlessly on 1&1 and Siteground…

I have tried Opera, Chrome, Edge, Firefox - all the same. Paused Cloudflare, but it didn’t help.
But I can log in on the Android app, for what it’s worth.

Any new ideas?

BTW, I just clicked on “Forgot password” and another screen shows up asking for username/email and below the new password and the new password again for confirmation. No email with a password-reset link. It looks like anybody who knows the URL and the username or email can reset the password. But I can’t, because I get the same error message as with a login attempt about cookies and proxies.

I have this problem too. Unfortunately, most of the discussion in this thread is too technical for me. I dont’ know what most of it means. Although I see some reference to the referrer header.

I used to use a Firefox plugin that blocks the referrer header. But I’ve switched to SeaMonkey, which as of yet, does not have such a plugin. But I still get the error anyway.

However, I did find a way around the problem (clearly by luck!).

When I see the login page, the URL in browser address field is twice longer than the field. Huge string of url and I have no idea what most of it means. But if I change the address to just the raw page address (such as h…ps://mydomain.com/stats) then I’m allowed to log in.

Can someone explain in a simple way, how I can fix this? Even with the lucky workaround, it still would be nice to just log in.

Thanks :slight_smile:

Edit - note that I’m still using 2.15 - would upgrade fix it?