Thanks for visiting the Community, @rahulraja.
The error 101 can be sometimes caused by various reasons. Here are a few ways on how to fix this:
Log in to your bank's website.
Check if your account is active.
Look for missed prompts.
If the issues persist, try signing into your QuickBooks Online (QBO) using a private browser (incognito). This will help us check if this is a browser-related issue.
Once logged in, try to manually update your bank in the Banking page to double-check. Here's how:
If it's successful, return to your default browser and perform a clear cache to refresh the system. However, if the same thing happens, try using other supported browsers.
Just in case, I'll add this article that tackles fixing banking problems in QBO: What to do if you see a bank error or bank transactions won’t download.
Please leave a comment below if you have any other issues or concerns. I'm always here to help. Have a good one!