Hello @rajagopal
This could be caused by several things. Possible causes may include:
Schema validation issues in the descriptor JSON
Atlassian not being able to reach your descriptor (e.g. ngrok tunnel issue, HTTPS problem)
Or even potential Marketplace conflicts (e.g. using the same app key locally as one already published) - not really sure here though.
…
Also worth noting: the Atlassian Connect platform is being gradually deprecated. You can read more about the official timeline and migration plans here:
Atlassian Blog – Connect End of Support Timeline and Next Steps