Using APP to process stacks/data from other apps?

Are we able to use APP to process stacks that were generated in other apps? For example, I had previously stacked 26 frames from Andromeda, but didn't have any real astro software so I did what I could, still wasn't satisfied. The only photo software I have is Luminar (which doesn't have any of the standard astro type tools) and GIMP. Ended up sending the .tif file I got from Sequator to a random dude on the internet, he processed with PI and was able to pull out a LOT more data that I could without astro software. So that was when I finally decided I needed astro software, hence me getting APP.

So now when I added another 17 frames to that batch, for a total of 43 frames of Andromeda, and ran it through the whole process that I could figure out in APP. After that I was comparing the new APP result (that even has more data) with the PI result from the Sequator stack and it seems like the Sequator stack had more detail that was able to be extracted. Is there any way I can open the .tif from Sequator into APP and process it to see if its a stacking issue in APP perhaps not combining all the data correctly or if its just a processing difference and maybe I just haven't found the right combination of tools/options/sliders to get this data to show up?

Every time I try to open the Sequator .tif file with APP it won't do it, unless there is a way to do it that I'm not finding. Any help or info would be greatly appreciated as I was hoping I would be able to do this with APP to at least compare data from various processes.