Sandisk ULtra 32GB USB no longer working

Hi there I have a Sandisk ULtra 32GB USB and it was working fine but now my Samsung S7 wont recognise it even though my Mac computer does. Can anyone help, in my phone when I troubleshoot it suggests to turn on the OTB in the settings but there does not seem to be anywhere in the settings on my Samsung S7 to do so, plus I did not turn it off. Any help would be appreciated Thanks

Did you format it? The 32GB drive should be formatted as FAT32 and readable by just about every OS.

Yes I have used it many times its my only means of downloading the pics in my phone when I am away from my computer. thanks for the suggestion…