Sso login: KRB5NegotiateAuth::doAuthentication(): An unsupported mechanism was requested

Hi, I configured access to the UMC portal by following the instructions at the link:

but trying to log in I am asked to enter the credentials instead of the management page. the following is reported in the logs (/var/log/apache2/error.log):

AH01215: PHP Warning: KRB5NegotiateAuth::doAuthentication(): An unsupported mechanism was requested (65536,0) in /usr/share/simplesamlphp/modules/negotiate/lib/Auth/Source/Negotiate.php on line 143: /var/www/saml/php-cgi

what am I doing wrong?

thank you.