Hi danielv97774392 ,
Would like to know which service you have purchased, if you have Acrobat Pro DC then go to this article :- Convert or export PDFs to other file formats, Adobe Acrobat
If have Export PDF service & on trying to convert the file over internet browser then would request you to please check with the different browser . Also please turn off Firewall & anti virus services.Please check is this happening with all files or with certain file.
You may also use Adobe Reader DC (Free Version) for converting the files , please refer to this Article :- Convert or export PDFs to other file formats, Adobe Acrobat