Upgraded router issues

This is odd and I have no clue what to do anymore.  We had a Arris TG1682G router and really weren't having any issues.  Yesterday while picking up a new cable box, the rep told me I should upgrade my router.  Sure, why not.  Newer technology.  Not sure what brand they gave me as there isn't any name on the box other than xfinity.  The rep told me to activate using the app xFi, if that helps.

Anyway, all three of our Samsung products (2 cell phones and 1 tablet) will not download or update any files in Google Play Store using WiFi.  It shows downloads available, but when you click to update or download, it just says either downloading or download pending.  That's all .  I also cannot access the Ecobee app.  Just gives me the main screen and that's it.  But they all work when I disable WiFi.  My tablet, which is only WiFi capable, won't download or upload unless I tether to my phone, which is not on WiFi.  I've cleared caches and data.  Restarted phones / tablet and router. 

My kids have Iphones and they CAN download updates on their phones, but it seems slower than the old router. 

Please help.  I may take the new box back and just reactivate, if I can, the old router.