Getting ppt files onto figma

Please help. I am trying to upload ppts into a figma board. I go through the steps and it just gives me an error. (see screenshot) I have also tried to import the files directly into the home page (not the board) and I can do this but it looses all my tables. Any ideas of how to do this would help. The only way I can figure it out is to copy and paste on slide at a time…

I have tried plug-ins but these won’t run. I have spoken to my IT team and they say that there is nothing at my end that should be blocking this. 

Could it be to do with my free account? Or that I am trying to work in a board that has been shared with me? (I am able to edit it in other ways though..)

Thanks!