It depends on the number of records as well as if the JSON is made available by the GST Portal for download.
Note: To check whether whether JSON is available for download, you may try to download the JSON from the GST Portal. If it shows a waiting period of 20 minutes or more, it means that the JSON is not being made available by the GST Portal for download.
The software keeps retrying if the JSON is not available for download from the GST Portal. That is the reason it shows as downloading from a long time.
You may try to download using OTP. That method is more effective for downloading from the GST Portal.
Note: To check whether whether JSON is available for download, you may try to download the JSON from the GST Portal. If it shows a waiting period of 20 minutes or more, it means that the JSON is not being made available by the GST Portal for download.
This error is from the GST Portal. Try to download again after a few hours. You may also try to download using OTP. That method is more effective for downloading from the GST Portal.
You can try downloading in the early hours of the morning or at night. The Portal is not under a lot of load during those hours.
You may also try to download using OTP. That method is more effective for downloading from the GST Portal.
Check whether GSTR 1 has been filed for that period. Most likely GSTR 1/3B has not been filed for the period because the taxpayer was a quarterly filer or is under QRMP. You can check the filed returns for the GSTIN with the help of GSTZen Taxpayer Search or GST Portal Taxpayer Search