TYPO3 Core

Hi,

after upgrading from working typo3 8.7.13 to 9.5.3 I am getting the issue:

No public key could be generated. Please inform your TYPO3 administrator to check the OpenSSL settings.

I am working locally: Upgrading the installation to the new version works. I can use the install tool to do all the changes. After finishing when trying to call the backend I get the login screen and when entering the login I get the error.

Any hints on this issue are welcome. openssl is installed and available with php.ini.
Security settings is rsa and 'rsaauth' => 'a:1:{s:18:"temporaryDirectory";s:0:"";}', is installed. as well as
'saltedpasswords' => 'a:2:{s:3:"BE.";a:4:{s:21:"saltedPWHashingMethod";s:41:"TYPO3\\CMS\\Saltedpasswords\\Salt\\PhpassSalt";s:11:"forceSalted";i:0;s:15:"onlyAuthService";i:0;s:12:"updatePasswd";i:1;}s:3:"FE.";a:5:{s:7:"enabled";i:1;s:21:"saltedPWHashingMethod";s:41:"TYPO3\\CMS\\Saltedpasswords\\Salt\\PhpassSalt";s:11:"forceSalted";i:0;s:15:"onlyAuthService";i:0;s:12:"updatePasswd";i:1;}}'.

When trying to logon to backend again I get a connection error no logon screen any more. Login to the install toll still works without any hints on problems.

Thanks for any help
Eckard.