As for the settings, I set all lightning-related to default/blank.
I'm using the 2020 March 18 Build (today's latest available build).
It seems I'm a little bit late can I get this new build this might be the issue that is why it doesn't work?
PM the link or the link posted above by DireWolfM14 is the one you use?
-snip-And let me ask if what will happen if I close my open channel? What will happen to my test coins?
I'm running it from source so, it's the same link of the 'zip' file you get from GitHub.
If you close your channel, the funds will be back to your mainchain balance;
if you
force-close it, the funds will be back after a day.
(may be wrong)
Okay, I'll try again, here's a request for 100 sats set to expire in 24 hours. I'll keep the client running all night.
I'm getting the same result when sending to a disconnected channel.
But it's not the same error when you try to send to a single PC with multiple instances of Electrum.

I'll retry it periodically or open another channel, might be a connection or routing issue.
Update: Eclair failed to send through lightning too, it worked for me, tried just now (
maybe your client was closed for some reason?).