Too many devices on my network for my plan?

I'll assume your Sensi requires the 2.4 GHz frequency, so is 2.4 GHz enabled on your Panoramic?  Also, I've read naming your bands (2.4 & 5 GHz) with the same SSID helps.

Other than that, I don't know.  A lot of subscribers report not being able to connect Internet-of-Things devices:  outdoor grills, bathroom scales, older network cards, etc.  I'm not sure of the specific wireless limitation of Panoramic (channel width, encryption keys, protocols, etc) but it's worth considering buying your own modem and router.  Gigabit service would not solve wireless incompatibilities.