Background color with gradient isn't working when generating via Mobile

[aningbo]

Whenever I generate PDF using my iPhone XS, the background color doesn't load. It just gives a blank white background!

This the CSS codes I tried but both shows blank background color!!

Note: This happens ONLY when I'm generating the PDF on my iPhone XS. Didn't test with any other phone. It works on my desktop version though as it should.

.thankyou__box.green {
  background: rgb(175,212,100);
  background: linear-gradient(90deg, rgba(175,212,100,1) 0%, #fff 100%);
  background: -webkit-linear-gradient(90deg, rgba(175,212,100,1) 0%, #fff 100%);
  -webkit-print-color-adjust: exact;
}
.thankyou__box.grey {
  background: #cbcbcb;
  background: linear-gradient(90deg, #fff 0%, #cbcbcb 100%);
  background: -webkit-linear-gradient(90deg, #fff 0%, #cbcbcb 100%);
  -webkit-print-color-adjust: exact;
}