Hey @Liibo,
For vectorfiles we have special requirements. You will find them here:
If your design already met our requirements and it’s still impossible to upload it, then just send me youe AI-file and I will have a look what could be the issue.
Regarding the question about FLEX: In your partnerarea it is not possible to set the printmethod to flexprint. Only the customer can choose this method via the personalise- Button if the design is a vectorfile.
I also recognized that you only uploaded a pixelfile so far. I couldnt find any vectorfile in your partnerarea. Besides that the uploaded png-file seems more like a shop-design than a marketplace design. But you havent create a shop yet. You can still add one ore more shops as new salespoints besides our marketplace.
Let me know if you need further help.
Best Rico