Well try not to blink 4head and they will not disappear

please help me where to go coupons that I have gathered

Were you in a event, where's an auto buy option if your own items aren't enough for level up? If so, you might have accidentally spent your coupons in it.

Hi,

You can submit a ticket with customer service giving all the required details and providing screenshots (including the server time and date within the screenshot) so that they can do an investigation regarding the coupons.

Please note that as mentioned, many upgrading features have an auto-upgrade option that can be selected which uses any coupons or ingots after your available resources are used until the item upgrades so please be sure to check this is not selected each time you attempt to upgrade anything.