Just posting my experience in case it helps anyone in the future and saves them 4 hours of relentless weeping with customer service.
I purchased a monthly (30 day) data pass 2 weeks back and was able to use it until this morning. Every time I tried to connect to xfinitywifi on my laptop I was brought to the sign in page. I sign in, but then redirected to the purchasing screen asking if I want a 2 hour, day, week, or monthly pass.
I already purchased a monthly pass, and verified it was active in the Account Info -> Manage My Devices and Passes screen. I called customer service and was told to 'Forget' the wifi connection, clear cache & cookies and restart -- everytime. It didn't work.
So after googling around a bit, it looks like the data pass is tagged to the MAC address of your Wifi network adapter. To troubleshoot, try this:
1- Press the 'Windows Icon and R' to launch the run window. Type 'cmd' to open the command prompt window. Type 'ipconfig /all' and verify the MAC address under 'Physical Address' field under 'Wireless LAN Adapter Wi-fi'
2- Verify the MAC address tagged under your data pass in the Manage My Devices & Passes screen. If the MAC address does not match the physical address in step 1, that's probably the issue
Some devices allow you to edit the MAC address of your device (https://www.groovypost.com/howto/change-mac-address-windows-10-why/).
Some don't and you might have to download some free software to change your MAC address.
Hope this helps!
Thanks for posting these tips, shaminaibr. If you still need assistance with your XFINITY On Demand WiFi pass, please reach out to me via private message and include your full name so I can help. You can click my name (ComcastJoeTru) to view my profile and send me a private message. Click "Send a private message" and private message me.
Since we didn't see a response from you, shaminaibr, this thread has been locked. Please don't hesitate to send me a private message if you continue to need help with this issue, or create a new post if you need assistance with anything else. Thank you.