Invalid Nonce error

-Agent leaves Phone Panel and SFDC Open overnight: 
Agents that receive “invalid nonce” might be leaving themselves logged in overnight. I.e. Logged into SFDC with Phone Panel open. Logging out of and closing all SFDC windows and phone panel and logging out of call center will resolve this. 

-Another reason might be SFDC permissions: 

One other reason that caused an agent to get “Invalid Nonce” is that they do not have the SFDC permissions to save the task against the selected SFDC entity. We can test this scenario by the following:

When an agent receives the error, he can try to add the data into SFDC manually against the entity, to see if he still receives a permission based error. This issue can be resolved by granting the appropriate SFDC permission to agents experiencing the issue.