failed to connect

i have an Ixpand mini 32gb,

i had some stuff in my flash drive but after deleting it it still showed the memory maxed out so i decided to erase it on my mac, fristly i erased it in an APSF encrypted format but later after realising its not supporting on my iphone i tried evry other format including the FAT format but still it wont connect, below is the error i keep on getting… if anyone knows why…THANKS

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.