Thank you posting, I have some information about the error you’ve received.
When this error occurs, it typically means that the image you’re trying to upload has been previously “optimized” with a lossy gif encoder. Our platform works with “lossless” encoding for gif images so this would be directly in conflict for our own optimization. In order for the image to be uploaded, it will need to be “un-optimized”.
To un-optimize the gif image, you could use a local image editor installed on your computer (there are great free options such as G.I.M.P. or Pixir), or an online service like ezgif.com(Please keep in mind that this is an external site not associated with Shopify in any way, and you must be aware that if you use an online service, you will need to agree to their usage policies and what this may imply for the privacy of image data uploaded to their servers. Be sure to read their Terms of Service).
If you choose to use ezgif.com, you can follow these steps: