Upon creating eWallet ShopeePay charge via API, you will receive 2 parameters which are:
"mobile_deeplink_checkout_url"
"qr_checkout_string"
As for the mobile deeplink checkout url, you need to open the url on mobile phone with Shopee App installed instead of desktop. If you open the link on desktop it is expected to return 404 error "it looks like something is missing" like below picture:
If you would like to open the link on desktop, you can use the qr checkout string instead, hence the QR Code will show up on desktop for your customer to scan it using their phone which has Shopee app installed.
You will need to render the barcodes on your end using a software package.