Using a mac with photoshop
In an ideal world, your use of a Mac and Photoshop with the Pebble4 printer would work fine. Unfortunately, you're presumably using a current OSX with a current release of Photoshop, and then attempting to print with a printer that barely supported Mac OSX when it was last manufactured in 2012. From our experience selling/supporting Evolis products since they first were offered in the USA, here's some things to try:
1. Create a 300-dpi .jpg image of your card design. Ensure it is sized as a CR80-card. Render the colors as RGB, rather than YMC. Then attempt to print the .jpg file to the Pebble with a different, more-simple program than PS. (ensure your margins are set to "0" all around (top, bottom, left, right).
2. If that doesn't work - download the cardPresso badge software (free trial) from their web-site. It works on Mac OSX, so you may get better results, as it is designed to work with card printers. Take your .jpg image (from step 1) and set it as your background image on a new card-design in cardPresso and try to print from there. (note you'll see a "cardpresso" watermark across the front of printed cards while using the trial version.). If this works, you can buy a copy of the basic version very inexpensively (particularly when compared to the cost of a Mac or Photoshop).
3. Do you have access to a Windows PC? If so, one with Win7 is preferred. Download and install the Pebble Windows driver, connect the printer, install the cardPresso trial edition (as in #2, above), create a new card with your PS design as the "background" image, and try printing from there.
Beyond these options, you have expensive ones, including getting a current-model printer that would be fully supported for the environment in which you're trying to use it.