We have a user using FrameMaker (FM) 2019/2017 that has issue reading files from SharePoint 2019 (on-prem) document library. The issue is that when trying to read the file(s) on SharePoint 2019 from FM client, the files is not able to render on FM. However, the same steps to read file on SharePoint 2013 it has no issue - able to render the *.fm file on FM.
Is it only one user that's having issues with the newer SP location or anybody who tries that newer version of SP? If it's everybody, I suggest you contact the FM folks - see https://helpx.adobe.com/contact/enterprise-support.other.html#framemaker for your Adobe Support options. I'd recommend using the firstname.lastname@example.org e-mail address as it reaches a team dedicated to Technical Communication Suite products including FrameMaker.
@Jeff_Coatsworth thanks for the recommendation for our issue. Regading who is having this issue is all FM folks accessing to the SP2019 server document library. We moved their contents from SP2013 to SP2019.