No results found in 'Archive to SuiteCRM'

We are using the SuiteCRM outlook plugin. Up until a few weeks ago archiving e-mails to SuiteCRM worked fine. However now when we try to archive an e-mail no results are found for any searches in the ‘Archive to SuiteCRM’. All of the modules are ticked and contacts definitely exist in SuiteCRM.
When we go on the settings on the SuiteCRM outlook plugin and test the login settings it reports that this was successful. We have tried installing the outlook plugin on different users computers and it also has the same results. This suggests that it might not be a problem with the plugin directly.

Many thanks for any help given