Specified Encryption Algorithm on Softether Server not Working

nano vpn_server.config

Edit the config file in the server, and look for this value:

bool Tls_Disable1_3 false

Change it to the following value:

bool Tls_Disable1_3 true

That will disable TLS 1.3, and the selected cipher will work again. You can even select RC4-MD5 if you desire.