Reason of failed review: Your solder mask layer is empty. Or there is no solder mask in your gerber file.
Suggestion:
1. If it is correct, do you want us to cover solder ink on whole pcb ?
2. Do you want us to make whole pcb open and no solder ink in pcbs?
3. If it is incorrect, pls update your file and send it to us.
BTW, we suggest you can write details on “other special request” so that we can avoid same problem. Eg: whole bottom side should be covered with green ink