Hi @BinhXuanNguyen
I understand your problem - main reason behind this is your theme , Are you using your custom/third party theme right ?
So here i would suggest you to change it to Luma theme and then check messages are showing or not !
If showing then enable your theme again , you manually need to identify in css from where theme developer has written display:none and that has to be removed from there
It will works , Hope it helps
if issue solved,Click Kudos & Accept as Solution