failed to connect

When you formatted it as APFS it likely changed the partition type to a GUID partition. You will need to reformat it as a Master Boot Record partition and use MS DOS File type for the file system. 

Here is instructions for formatting on mac. If you have the latest version of mac OS in the upper left corner of disk utility click the drop down for view and select show all devices. 

https://kb.sandisk.com/app/answers/detail/a_id/203/