I'm not sure what the problem is but Collector is not recognizing the TPKX file that I created to uses as off-line basemaps on either my Android device or on Windows. Are there some sort setting that need to be changed? They are both recognizing TPK formats though. Both Tile Packages were created using ArcGIS Pro v2.3. The Windows Collector version is 220.127.116.11 and the Android version is 18.0.3, build 1033. I tried uninstalling and reinstalling the Windows version but alas, same issue. Also if its of any use the size difference between the two formats is quite large, the TPK file is only 6MB while the TPKX is 1.2GB. The extents and scale level (15) to create each file were identical. Any suggestions?