C3700 problem with spectrum modem

> Worked fine with previous modem, [...]

   _What_ did?  What was "previous modem"?  Where is it now?

> [...] got new modem today [...]

   Is that the C3700 or something else?  Note that the C3700 is a
modem+router, not a simple modem.  Also, using two modems on one cable
connection is generally not allowed, and using a C3700 as a router
without a co-axial cable connection is generally not possible.

   What, exactly, are you trying to do with these two devices (whatever
they are)?

> [...] and will not allow me to sign on.

   How, exactly, does what stop you, when you do what, exactly?

   None of that is not a useful problem description.  It does not say
what you did.  It does not say what happened when you did it.  As usual,
showing actual actions (commands) with their actual results (error
messages, LED indicators, ...) can be more helpful than vague
descriptions or interpretations.

> [...] see attached photo. [...]

   I can't (yet) see your pictures.  In-line images must be approved by
a moderator before others can see them.  The time required varies.
Attachments have no such limitation.  Of course, attachments have their
own one-per-message limitation.  Copy+paste (of plain text) is your
friend.

   What are your devices?  Maker?  Model number?

   What, exactly, is connected to what, exactly?  (Hint: If a device has
different types of Ethernet ports, then "connected to device" is not
enough detail.)

> [...] have spent hours online with spectrum today [...]

   I heard none of that conversation.

> [...] I am wondering if it is a problem with DHCP interference [...]

   I can beat that.  I'm wondering what you're doing with what.

> [...] 9 devices in the house and the only one can use is hooked up to
> ethernet. [...]

   Swell.  "ethernet" to _where_?  From where?  How many modem, router,
modem+router gizmos have you, which do _not_ allow an Ethernet
connection?

> [...] any help would be appreciated!

   You first?