Can I buy coins if the transfer market of my account is not open on Web APP?
Unfortunately not, ALL coins delivery is made on Web App, not only on our website, it works the same way on any other coins store. You can get the market open by playing games though.
Play 6 matches daily, finish the first two daily objectives(Play 2 Matches, Win 1 Matches), get the season progress, objectives, milestones and foundations task rewards, open all the packs you get, keep playing like this for 5-6 Days, you will gain access to the Transfer Market on FUT Web App.
Please remember, this is the way how most of players get their market open, but not works for everyone 100%, cuz the efforts you need to make to get it open differs, depends on the current situation of your account.
It takes some efforts to get the market open on web app, but playing games is the only way to get it open and buy coins, it works the same way in any other coins store. Let us know if you need any help.