Check you have Windows time synced to local real time.
As a test disable AV and firewall. Reboot machine.
In Navigraph Hub make sure you are running Hub v.1.2.24 or later and are in the MSFS 2020 tab. Remove and Install Navigraph SimBrief Dispatch MSFS v 1.3.2:
Start MSFS 2020. In SimBrief Dispatch sign out, then Sign In to SimBrief Dispatch using the QR Code. Check your email for a code. Enter this.
You should now be signed in to SimBrief Dispatch.
Cheers
Ian