PayPal Checkout Sandbox – "The payment request was refused by PayPal" on iPhone

-- HikaShop version -- : 6.1.0
-- Joomla version -- : 5.4.0
-- PHP version -- : 8.3.0
-- Browser(s) name and version -- : Safari 26.0.1
-- Error-message(debug-mod must be tuned on) -- : The payment request was refused by PayPal. Please click here to return to the checkout.

Hello HikaShop Team,

I am currently testing the PayPal Checkout integration (Sandbox mode) in my Joomla / HikaShop setup.

The PayPal Checkout (Sandbox) integration works perfectly on desktop browsers (Chrome, Edge, Firefox).
However, when testing the same checkout process on iPhone / Safari (mobile) or iPhone/Chrome, I receive the following error message after confirming the payment in PayPal:

“The payment request was refused by PayPal. Please click here to return to the checkout.”

After this, PayPal redirects back to the shop, but the payment is not recorded, and the order remains “unpaid.”

Observation

It seems that the PayPal sandbox refuses the redirect back to HikaShop checkout only in mobile Safari/Chrome (possibly due to stricter cookie / session handling).

Desktop browsers are unaffected.

Question

Could you please confirm:

1. Whether the current HikaShop PayPal Checkout plugin already includes full support for mobile Safari (iOS) in Sandbox and Live modes?
2. Is there any workaround or setting I should adjust — e.g. Landing Page = PayPal, Redirecting after finishing = Yes or any specific Return URL that should be added manually?
3. If this is a known issue in the Sandbox API, is there an ETA for a fix or an alternative way to test iPhone payments successfully?
4. Could the issue be caused by the PayPal in-context popup window on mobile devices?
   → If yes, is there a way to disable the popup behavior (so that PayPal opens in a full browser redirect instead)?