r8000p dropping wifi connections

I have a r8000p with firmware v1.4.4.94 and it is attached to a xfinity modem/router. the xfinity router has 15 devices attached to it, mostly wired. I have called xfinity to check upload and download speeds and they are very good.  I started noticing a few weeks ago my wifi connections were dropping off of the netgear router and I was not able to login onto the 2.4 with my laptop. This is setup in my small business. I only have 14 devices saying it is currently connected to the net gear router and 4 of those are wired the rest wireless. I can connect my laptop to the 5g-1 but it will not let me connect anymore devices to the 2.4.  I first started noticing this when my credit card machine would go offline and I would have to reboot the routers / cc machine for it to get back on the wifi. 

I have had this router for almost 2 years and it has worked with no issues until recently. every morning it seems to grab whatever the first connections are for employee cell phones or whatever then it kicks other wifi computers off or does not let new connection to connect to the 2.4 after 14 connections made. My network or equipment has not changed so not sure why I can only connect 14 total devices through 2.4/5g-1/5g-2.  

How do I get more connections out of this router?