Hi
I try to install allpay
But when i do composer require --prefer-source mage2pro/allpay:*
It’'s show
Nothing to install or update
Package fabpot/php-cs-fixer is abandoned, you should avoid using it. Use friendsofphp/php-cs-fixer instead.
So, it looks like the mage2pro/allpay composer package is alredy installed in your system by somebody.
That is why Composer writes «Nothing to install or update».
The question is who did install it and by which means he did it.
Does the Magento root composer.json file contain the mage2pro/allpay package declaration?
Maybe you ran the composer require --prefer-source mage2pro/allpay:* command twice?
If you have already successfully implemented the steps 1-7 of the installation instruction, then I recommend to consider the step 8 (the package installation) as implemented too, and do the steps 9, 10, and 11.