Hey there, ron118. Let's get this working for you.
It's good you've performed some troubleshooting steps beforehand. Let me help further and get this sorted out.
When a browser stored a lot of caches, it could cause problems like latency issues. As an initial step, you can press the F5 key on your keyboard to refresh the page.
You may also try accessing your QuickBooks Online account using another supported browser.
However, if you're still getting the same error, I'd suggest getting in touch with our QuickBooks Support to have this investigated.
Please be reminded that our Support Team is available from 6:00 AM until 6:00 PM on weekdays, and 6:00 AM till 3:00 PM PT on Saturdays. Here's how to contact us:
1. Click the Help (?) icon.

2. Choose Contact Us.

3. Enter a brief description of your situation in the What can we help you with? area, then click Let's talk.

4. You'll be presented with a few options for connecting with Intuit. Select Get a call.

In case you need some references about how workflows work in QuickBooks Online, you can scan through the following resources below:
Use workflows in QuickBooks Online Advanced to send reminders.
Create custom workflows in QuickBooks Online Advanced.
Let me know if there's anything else you need. I'd be more than willing to give you a hand.