Impossible to format Sandisk SSD

[Micka88]

Really strange that I cannot format external Sandisk SSD drive. Disk utility - unmounting forever...

I had to connect to to Windows PC to format it at least to exFAT that worked immediately. But I want to format it to APFS which is somehow impossible.

How can this happen and how to fix it?

 

[greenmeanie]

Use Windows DiskPart to totally clean it.

 

[Minipudding]

Sometimes macOS can be a bit finicky with wanting to accept and engage with new "non-Apple" disks due to weird MBR/GPT and similar. Here's an "advanced" last resort method to fix this directly in macOS instead of booting into Windows or GParted etc. by zeroing out the start of the troublesome storage medium:

First, open your terminal and identify the disk number with diskutil list. Be sure to identify the correct disk here, so you don't accidentally proceed against your internal disk.

Then, in the terminal: sudo dd if=/dev/zero of=/dev/rdiskN bs=1m count=16 conv=fsync where "N" in "rdiskN" is to be replaced with the disk number. If you are running as an unprivileged user you will first have to su <your admin user> before running sudo dd ....

Remember to identify the correct disk number for this procedure or you will lose the contents of one of your other disks.