Thank you Pavel for your advise.. Actually with your suggestion of "debug software restart process management-server", did not bring any change as the error continued, hence I tried to restart the web-server process using the command "debug software restart process web-server" as its the web related process post which I am able to login to Panorama normally.
Infact the documentation from "How to Restart the Web-related Processes - Knowledge Base - Palo Alto Networks" was helpful in this case.
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