Data Import suddenly started getting An error has occurred message

Hi,

I have been successfully using the data import function, and all of a sudden I have started to get the message

An error has occurred. 

Try this action again. If the problem continues, check the Microsoft Dynamics 365 Community for solutions or contact your organization's Microsoft Dynamics 365 Administrator. Finally, you can contact Microsoft Support.

I have tested using import templates for a contact, and the error still occurs regardless of the templates or entity.

I have cleared cache

Not sure what the problem could be and why it just started, any advice much appreciated