Step1: Check antivirus and the firewall is disable.
Step2: System Date and Time should be proper.
Step3: If you are using BSNL network for data uploading process then please connect another net connection for the same.
Step4: After changing the connection start the server and upload the data. Issue will get solved.
If issue persists, please generate the SOLAR ticket with following details.
Learner Code-(those are facing issue)
Screen shot of the issue-
Updated mobile number.