Remmina suddenly stopped working !!

After an update the Remmina Desktop client stopped working . All RDP sessions were not connected.

If this is NOT a configuration or application error (missing libraries, corrupted build etc) then the reason will most probably be the stored encryption keys. These keys are either SSH_keys or RDesktop keys exchange by Remmina and the remote host the first time connected.  

Based on your Remmina installation (rpm,deb or snap)  the keys can be found under your home directory in a folder called .remmina  (the . in front indicates a hidden directory) .

If you are using a snap (default in Fedora Linunx) then the folder you are looking will be :

/home//.var/app/org.remmina.Remmina/cache

How to reset it ? 

Just remove everything under the cache directory.