I’m jumping in to suggest possibly your d/l s contain more than just the design itself. Your machine cannot open zipped files.

Hmmm, it might be the USB format... I have to use FAT32 for mine...the NTFS format will not work on my machines... Perhaps that is the problem???

I'm glad you asked this. I've had some issues with brand new USB sticks

many machines do not read usb sticks if they are larger than 16 GB

I have a couple usb sticks that my machines won't read. Don't know why. Maybe the brand, although I have many brands. Have you tried deleting everything on the stick and then dragging or sending the format you use over to the stick?

You probably already know this, but here’s a thought…<br /><br />
On the USB sticks that work, did you place the design files in a folder? Sometimes there is a requirement to load those files to you machine from a folder/sub folder on the USB. I found some info re: EMBf5 format, but the process is slightly different depending on which model of machine you are using. Take a look at the article in the link below. Scroll down through the pages to find your machine model. Good luck.<br /><br
https://www.janome.com/contentassets/0e240947517041e6bcd5423fca4020c4/transferring-designs-to-usb-stick-or-ata-card-no-software1.pdf

Some USB sticks are just tempermental!!!! I have two that have to be pluged and unpluged twice or more before they will work..... Good Luck

Usually the stick has to be formatted for embroidery use. Both my Janome 4 nld as my Ruby use the same files.. Made a screenprint of one of my embroidery sticks, see the red stripes, ignore the remainder. The designs go into the EMB file.
Some embroidery software enable formatting the stick the right way; if not and you have a stick that came with the machine, just copy those files, empty the EMB file and put the new files in.

What machine are you trying to use them on?

I have tried everything. I have looked carefully at all the sticks I am having trouble with. They are all old ones, up to 8GB. I think most of them were ‘handouts’ at various functions my daughters attended. They all load but my machine is just not reading them. I will just have to use all the ones I have.

My Ruby Viking will only read Viking usb. And they or the older one . My understanding Viking no longer have them. I bought a external floppy drive load my designs on floppies then the machine will read the Designs - hope that makes sense

There may be a couple of different reasons why they are not working, one reason is that they may be corrupt, as they are old this is very possible. Another reason is that there are different files systems that they can be formatted to, there are NFTS and FAT32 and exFAT, there may be others as well, but I have seen USB devices that have video files on them just not work on television if they are formatted to the wrong file system, you can choose which system it is when you are formatting them.