Why login only possible with Tor?

Why can I log in only using "Tor"-Browser? Usually I did it with Firefox, but also Chrome and other browsers answer with
"Fehler: Netzwerk-Zeitüberschreitung" (too long to answer)
I tried to do things that "Firefox - Help" proposed, but still no login possible!

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Grüße,
Robert

K8200 mit Original-Druckbett, umgedreht, unten mit Kork isoliert, oben Glasscheibe m. Wärmeleitpaste dazwischen, 24V m. SSR gesteuert.
Doppel-Z, Tr 8 x 1,5, mit Riemen getrieben; von Federn gehaltener, frei schwingender Druckertisch, höhenverstellbar.
Früher: Merlin-Hotend (zu friemelig für meine alten Augen), jetzt E3D v6

Schade, das es [k8200-wiki.de] nicht mehr gibt!

Your country is censoring the internet perhaps?

Chrome and Firefox work fine directly

try some basic network debugging, traceroute,ping and nslookup etc (how depends on your OS)

I have noticed the same from time to time. It seems around every full hour, there is a traffic jam in the atlantic cable. 5min later everything is OK.
German or EU websites work as usual.