For some reason all of our saved suppliers that we have built up over the last 5 years have dissappeared, has anyone else had the same issue?

Welcome to the Community, Craig.

I'll help you resolve the issue of being unable to see the suppliers that you have added over the last five years in QuickBooks Online.

If you can't see them at the suppliers' page, you can start by checking the Audit Log to see if there are actions made with suppliers.

If there's none, I recommend running a Supplier Contact List report to see if those suppliers are still on track.

Otherwise, let's perform a browser troubleshooting. The stored files in your browser are typically the source of unexpected behavior or failures in QBO. Your cache saves the files from many websites you visit, so you can quickly load the pages the following time. The browsing speed of websites like QBO may be impacted if the cache is retaining too much data.

It's a good idea to check for issues brought on by a full cache when browsing anonymously because doing so prevents the cache from recording your browsing data. You may also try to use other browsers.

• Chrome: Press Ctrl + Shift + N
• Internet Explorer and Mozilla Firefox: Press Ctrl + Shift + P
• Safari: Press Command + Shift + N

If the steps above will not work, you can use supported browsers as an alternative.

If the given procedures are successful, I advise you to clear the cache in your browser to avoid utilizing outdated forms, safeguard your data, and improve the performance of our programs on your computer.

If the issue persists, I recommend contacting our Customer Care team. You can request for a screen-sharing session so they can investigate further the reason of this issue. Go through this article for more details about the process: How to get help with QuickBooks. 

For future reference, you can read these articles about managing supplier transactions in QuickBooks Online:

• Manage outstanding balances for customers and suppliers in QuickBooks Online.
• Enter supplier credits and refunds in QuickBooks Online.

Don't hesitate to comment below if you have questions about managing suppliers list in QuickBooks Online. I'm always here to help. Have a great day.