Hi Laura,
Since the only difference between your test site and your live site is the server it is being hosted on indicates that the issue is most likely caused by your hosting environment.
Some of the possible reasons there is an error in your portal:
A. Most Likely
- A conflict with another DNN module in your portal being poorly written and could be the cause of the issue
- DNN portal issues – this could be caused by upgrading your DNN portal to a new version, corrupt dlls or many other things.
- Incorrect web.config configuration
B. Less Likely
- SSL issue
- IIS Config issues
- URL rewriting
- Security software blocking
- etc, etc
Hope this helps!