hotspot login page issue

hi,

I have a CCR1036-12-4S running router version 6.3. I have already configured hotspot and it is serving 400 - 500 users per day. The issue that i have is when i let the hotspot run for 6-7 days, suddenly the hotspot stop to assign the login page to the user thus make the user unable to get the login page. I have to restart the device, then the hotspot back to normal, but after 6-7 the problem return again.

May i know what is causing this issue? Cause the user is able to get the ip address but unable to get the login page.

Thanks.