Hi Dominique and welcome to the forum 
I think you must be referring to a “micro SD UHS-1” (manufactured by SanDisk). Not SSD (which in computing usually means “solid state disc”, used in PCs and other computers). So we’re talking about a “SD card” or memory expansion card suitable for phones and other small devices.
Despite the existence of standards, such devices are not always compatible. You may be interested to know about this topic which lists SD cards known to work well (or not!) with the FP4. You’ll notice that people have logged problems with the 1TB UHS-1.
Using SD cards to expand internal memory is no longer recommended by the community. It’s preferable to use them only as portable (external) storage.
Make sure this small microSD card is properly inserted.
The specifications of the FP4 indicate compatibility with SD 3.0. If you think the card should be compatible, I recommend you contactsupport.