@Bart35 Frontier Fiber service usually has an ONT and an eero router.  Can you confirm you actually have a "modem", or is it the ONT maybe?

  @Bart35 Did you try rebooting the ONT?

  @Bart35 Yes, and that helped. Everything looks okay now. Thanks for the help. Much appreciated mm

Bart35 wrote

I've been using a Deco X55 Mesh system with a 500 Mb Cable signal with good success.  However, after switching to a Frontier 500 Mb FIOS my internet speed has dropped to 150 Mb. The signal coming into the FIOS Modem has been confirmed to be 500 Mb so the holdup must somewhere on the Deco side.  I assume the problem can be solved with a modificatiom of the Deco Network settings.  If so, can someone please tell me how I can do this?  Any help will be much appreciated.