Are you able to access the portal's web app builder at all? Can you create new web apps? Or is it only existing web apps that will not open from the app overview page>EditApplication?
If you still cannot edit the app, you could try is this:
Get the item id of one of your portal hosted WABs. Go into the portals content items folder and search for the item:
D:\arcgisportal\content\items\your_long_id_item_number
The first file in the 'your_long_id_item_number' folder is the json config file for the wab application. I have an existing application I built at Enterprise version 10.6.1. The very top of the json config file looks like this:
{"theme":{"name":"FoldableTheme","styles":["blue","default","black","cyan","green","purple","red","yellow"],"version":"2.8", . . .
it looks to me like the pair "version":"2.x" may be missing from your config. Maybe you had a custom theme? So depending on when you built your apps in the Portal Web App Builder will determine what version it is. For Enterprise 10.6.1 it was version 2.8. For the latest 10.9 Enterprise the wab version is 2.19
https://developers.arcgis.com/web-appbuilder/guide/about-versions.htm
Maybe that will work, I don't know. I've never tried.....