Mac mini M4 not recognizing SSD via Thunderbolt port

I'm guessing you over loaded the bus. You can check in the system report for current draw. Get a powered hub and connect some hardware to that. I have a powered hub on my M4 Mini because when I attempted to connect another SSD to one of the TB ports I got a message that it requires more power and was not recognized. A powered hub solved the issue.

Verify with the manufacturer that the enclosure and the SSD you put in it are compatible with Macs in general and specifically for the M4 Minis.

Not all combinations of enclosures and NVME SSDs play well with any given computer. This is a common issue with both Macs and PCs. Some combos work well on one computer and when used on another computer they work sporadically if at all.

Personally, for a USB based enclosure, I have found that Sabrent combined with Samsung or Sabrent SSDs to work well. For Thunderbolt/USB4 enclosures/drives I tend to stick with OWC. They are sometimes a bit pricier but OWC is a Mac centric vendor so they test their products on Macs.

Hokyzlin wrote:

The SSD is enclosed in an external case Axagon EEM2-20G Armored Box for M.2 NVMe SSD up to 20 Gbps USB-C 3.2 Gen 2x2.

FYI, Macs do not support USB 3.2 Gen 2x2 ("up to 20 Gbps")

However, the Mac and drive enclosure should be willing to negotiate the use of USB 3.1 Gen 2 ("up to 10 Gbps"), whether you connect the drive to a multi-purpose USB-C port in the back, or a single-purpose USB-C port in the front.

The description of the drive says, in part

"Podporované operační systémy:

• Windows 7 / 8.1 / 10 / 11 a novější, macOS, iPadOS, iOS, Linux, Chrome OS a Android."

which Google Translates says is Czech for

"Supported operating systems:

• Windows 7 / 8.1 / 10 / 11 and later, macOS, iPadOS, iOS, Linux, Chrome OS and Android."

I have the same issue. Wanted to use the NVME to use in an OWC Powered HUB. The PC allowed troubleshooting and success. However my MAC Mini M4 (new to Apple) does not seem to have a troubleshooter. If you know where I can find that, it would be much appreciated.