Thanks for your bug report. It looks like this is due to Item 9 in
versions.txt, the fix for the OpenSSL v3.x slow-down issue.
The issue in the latest version is that, if cacert.pem is not loaded, it is not using the Windows certificate store as a default. Since mIRC installs cacert.pem by default, this should only affect users who have manually removed/disabled cacert.pem for some reason.
The main reason why cacert.pem was originally added to mIRC was that the Windows certificate store, many years ago, was not including all of the certificates that cacert.pem included.
However, since some users create custom certificates that are only stored in the Windows certificate store, mIRC should load that as well.
This issue has been fixed and a beta will be released soon for testing.