Quote Originally Posted by lat9 View Post
I've gone to the test site (https://vinosdefrutastropicales.com/zc157_bs4) using my sister's iPhone, added an item to the cart, went to guest-checkout and the DOB (05/31/1970) was accepted.

I have no idea why your devices' entry is different, but if you'll do the same as above with the devices that are not accepting the date-of-birth that will help me 'see' what is going on.
It seems this link that you mentioned uses different template from classic. I checked on the mobile and it does not pop the DOB , it asks to enter the DOB by typing it , but in my case the DOB cannot be typed, instead the date can be chosen from pop up. I believe the templates are different. So I suggest you use Classic Template to see how it goes, if you are able to enter DOB then if it goes to next step!.