Connection fails when frontend uses nonstandard port

[mwt]

When I try to use a non-standard port on my backend, I cannot connect using the pagekite frontend. I get the following error:

>>> Hello! This is pagekite.py v1.5.2.201011.                   [CTRL+C = Stop]
    It looks like your Internet connection might be down! Will retry soon.
     - Check whether you can ping pagekite.net or google.com
     - Check whether `pagekite.mwt.me` can be looked up in DNS
 << pagekite.py [down]     No kites ready to fly.  Waiting...

yet, curl pagekite.mwt.me:14678 gives me the "pagekite for pagekite.mwt.me:14678 is unavailable at the moment." page. So I am able to connect to the frontend via the backend. I just can't get pagekite to recognize it. I've tried both with Python 3 and Python 2.

Frontend details

Here is my frontend config (~/.pagekite.rc):

isfrontend
host=0.0.0.0
ports=14678

protos=http,https,raw
domain=http,https,raw:pagekite.mwt.me:secret

rawports=virtual

and log:

tunnel_socket_blocks=False; optfile_/home/matthew/.pagekite.rc=ok; started=/home/matthew/bin/pagekite.py; ll=0; optfile_.SELF/defaults.cfg=ok; ts=5faa2b01; argv=; python=2.7.18 (default, Oct 16 2020, 00:11:15)  [GCC 9.3.0]; platform=linux2; version=1.5.2.201011; t=2020-11-10T05:54:09; ca_certs=/etc/ssl/certs/ca-certificates.crt; send_always_buffers=False
id=s1; ll=1; listen=0.0.0.0:14678; ts=5faa2b01; t=2020-11-10T05:54:09

Backend details

I've just been running:

./pagekite.py --clean --frontend=pagekite.mwt.me:14678 --service_on=http:pagekite.mwt.me:localhost:80:secret

I also have some config files that say the same thing in more lines.

Edit: Running the backend command does not add lines to the frontend log. So, I don't think that a connection is even being attempted. The curl command does add a line to the log.