I have found the solution when I searched with the error number:
UpdateLib delivers error 537.
In Avira Control Center, turn of Proxy Settings.
Start Avira Control Center
Go to Extras ? Configuration
Where applicable: Activate the Expert mode (version 2013 or older)
Click PC Protection ? Web server ? Proxy settings
Click the option No proxy server if you do not use a proxy
Click OK to apply the configuration
How ever I have not changed that setting myself, so I am still vigilant since I don't know why before five days it did function, and now it did not. Why could that be?