I finally discovered and fixed the problem with the help of a colleague. This was a pretty harmless problem with server time in our test system, which was 2 hours behind. This led to the fact that cookies were set in Internet Explorer with the expiration of time in the past, as a result of which the login always failed. The amazing problem was that cookie expiration was disabled only in Internet Explorer, with every other browser having the correct expiration date.
, : NTP