Hey there Lou10,
 
Thanks for reaching out to us here. QuickBooks Online is a great tool to have, it allows you to connect your bank accounts so that you don't have to manually enter transactions. It's important that your Clients are able to connect their bank account without running into any issues. I can provide some information about connecting back accounts to QuickBooks Online.
 
It may be browsing data on your system that is preventing the software from doing what it is supposed to do and not being able to leave your bank connected. Here are some steps to resolve issues that are caused by browsing data:
If they are still having trouble keeping their account connected to QuickBooks, I recommend reaching out to the support team outside of the Community. They'll be able to verify your account details in a secure setting as well as view your screen to see what may be causing the issue. You can reach out to them using one of these methods:
 
Schedule a Callback or start a Chat: click (?)Help in the upper right > type and enter "Contact support" into the QB Assistant > click Contact Us > explain your situation > click Let's Talk > choose Get a callback or Start a Chat.
Social Media: Facebook and Twitter
 
If you have any other questions, feel free to reach out here.