Website Checkout button not visible on Samsung On5 model

[mjobrr]

My website is responsive website, it is opening on any hanset without any issue, my website have commance site, buy has seletct the service then check for payment, but Samsung On5 model checkout button is not visible on screen, due to this user is unable to pay.

But this checkout facility is happen in Samsung other model,

could you suggest any upgrade or fix from your side.