I had the same problem but I found a solution just now.

While processing the withdrawal for the second time, I deleted the GCash number then added the same info again.
It worked naman. Natanggap ko na sa Gcash yung money.

"I'm not sure if this step is necessary or not" but before ako nagwithdraw, I also made sure that on my Account Info, my cellphone number (same number with GCash) is verified through the code that was sent to my number.

Try nyo lang.

Hello.. Nakapagwithdraw na po ba kayo Skrill to Gcash? Rejected parin kasi sa akon til now.. sa tingin nyo sa g-cash kaya prob o sa skrill?