N450/CGV3000DV2 - L2PT error when connecting to VPN

Connecting to employer's VPN via wi-fi on N450 gets error: L2TP connection attempt failed because the security layer encountered a processing error during initial negotiations with the remote computer. 

This problem started on Friday. IT team tried to resolve, and until they could check everything out, they suggested that I try through my mobile hotspot. I was able to get onto VPN via my phone's mobile hotspot. 

On Monday, I tried to connect via mobile hotspot and got the L2TP error. IT did a lot of troubleshooting and checking into everything on their end and was unable to resolve but could confirm that everything on their end looked ok. Advised to call Comcast. Comcast said there is nothing on their end stopping this and that I should check my router. Employer has checked everything on their end. Comcast won't check my router because I own it. Today I connected via ethernet and could get onto VPN. Then disconnected ethernet and tried via wi-fi and it connected to VPN. After a couple hours, the VPN disconnected and I cannot reconnect to VPN via wi-fi. I get this same error.   

Can anyone help? Thank you!