This applies to Affinity Photo edits when using multi exposure stacking, File/HDR Merge. It appears Affinity Photo sometimes resizes the 360 photo after it merges the photos and the export is not exactly 2:1
For example instead of 6912 x 3456, the exported photo may be 6910 x 3455
Testing by importing into Google Photos shows Google does not recognize it as a 360 even after editing the meta data. Only after resizing the exported photo to 6912 x 3456 does Google see it as a 360 photo.
Oddly enough Facebook uploads and the Ricoh Theta 360 viewer and the Gopro viewer both can view the images as 360 even though the size is not exactly 2:1
Something to try if nothing else is working.