Fortigate has recently release firmware upgrades that require a higher level of encryption (negotiated) with UVexplorer's SSH client.
If you've upgraded to Fortigate firmware v 7.2.7 or higher and you implement userid/password to ssh to the device, then we recommend updating UVexplorer v125.
v125 has resolved this encryption issue on Fortigate devices.
For more information or assistance on this issue, please contact the Support Team at Support@UVnets.com.