If the GCash app said verification failed during signup because your photo or ID had issues (like being blurry, poorly lit, cropped, or not matching your details), you can take new pictures and upload them again in the app. Make sure that your face and the whole ID are visible and that the picture is well-lit.
You can usually resubmit through Profile → Verify Now in the GCash app for 10 days. If that time closes, you might have to start the verification process all over again.
Before you try again, make sure the name and birthday in the app are exactly the same as on your ID. Also, make sure your app is updated, that you can use the camera, and that you have a clean background and good lighting for pictures.
If you still get errors after trying several times or don't see any change after a few days, you could file a complaint on Xolvie to get people talking about it and try to get it fixed.