Hi Dave,
The error that you shared is actually an alert. It's meant to direct you to your Exception log to read the actual error. It's a bit like a generic warning light that might come up on a vehicle's dashboard - the light itself could be alerting you to any number of things.
If you can access your hosting environment, such as via SSH, the Exception log should be in the following directory: var/log/exception.log.
Usually, the errors that you find in the exception log will require a web development fix of some sort, although depending on the error, your web host may be able to help with some kinds of issues (even if it's just a temporary fix).
Best of luck!
