Issues connecting to dataset

When I download a report (my own or created by another user) I am suddenly getting the option to download a copy of the report and data, or a copy of the report with a live connection to data online. 

When selecting the first option I am able to see the report as normal but when trying to transform I get this:

When selecting the option with the live connection I am getting this error message:

All of the reports that are now giving me this option are all connected to the same tabular model, which I have permission to access and can access correctly when opening a existing or new report. I have downloaded them previously without issue as well.

I am also having an issue with reports that are saved on my drive, that this morning worked fine. If they have a live connection I can no longet access the data and get the add model pop up as above. For ones that have multiple data sources and therefore don't have a live connection to our tab mod, I have some that work fine and some that don't. I have had other users test their reports and they are getting the same issues.

Any help is greatly appreciated.