Have been getting a error message "Something went wrong, we are working on it" whenever I am generating GSTR1 report for last 3 months Plz explain and rectify ?

You made the right choice in letting us know about this,

I can help fix the error you're getting when trying to generate GSTR1 report in QuickBooks Online (QBO).

The error you're getting can be caused by an old cache piled up on your browser. To fix this, let's perform some basic troubleshooting steps and start by logging into your QBO account using a private browser window.

Try these keyboard shortcuts depending on the browser you're using:

• Google Chrome: press Ctrl + Shift + N  
• Mozilla Firefox: press Ctrl + Shift + P
• Safari: press Command + Shift + N

Once logged in, go run back the GSTR1 report. In case you need reference, let me share the steps on how to pull the report below:

1. Go to the Reports on the left menu.
2. Under GST returns, choose GSTR1- Summary of outward supplies report.
   
3. Customise the necessary filters like the Report period and Accounting method. Then, click Run report.
   

For additional information about managing GSTR1 report in QBO, check out this article: Know more about GSTR-1 Summary and Detailed reports in QuickBooks.

If it works fine in the private window, clear the browser's cache to remove the log files and start with a clean slate. Otherwise, you can try using other supported browsers to be thorough.

Be sure to get back to me if you have follow-up questions. I'm always happy to help. Have a good day!