Hi, I'm Nathan.Sorry to hear that you're having trouble with this but I'll do my best to help you.
Can you tell me a bit more about the problem please:1) Is this a dedicated fax line, or a shared voice/fax line?2) Is this a landline from the local phone/cable company, or a VOIP service (vonage/magicjack/etc)3) Do you have dsl service on the same line?
4) Are you able to RECEIVE faxes?
Okay you mentioned "other fax" can you tell me more about that?
So these are on separate lines/numbers (not sharing the same line just on different wall jacks)?
Okay, we will need to do a bit of testing here.
Can you either plug a phone into the wall jack (just a regular corded/wall phone) that is currently used by the downstairs fax, or plug the upstairs fax into the downstairs jack, and try to make a call or send a fax that way?This will help us to isolate if this is a line fault or an issue with the fax machine itself.
The sleep mode is just an energy saving feature and would not prevent it from sending.
That's fine, you can test this when you are able and get back to me after.
Do you need more help with this?