Maybe a stupid question, but did you actually research Alliances and did they have it? I noticed something similar happen last night when I was a few turns away from an influence victory. I switched at the last minute to research alliances, sent them both the tech, next turn they were close and happily allied with me giving me effectively a double win when I clicked the next turn button - although only the Alliance victory video played.

Other than that, I think long term peace and prosperity between your civs, non-conflicting ethics, not too close borders and lots of trade routes is the answer. Giving them gold is probably best done in a big lump sum and I'm sure they value techs higher - especially if you dump a load on them in one go.

Well then, sorry I cant help you. Did you look in the report to see what negative feelings they had for you? The few things I can think of is your ethics, your alarming influence, your military strength being much lower, them being militaristic, having close borders and a "we know what you are doing" (even when they dont!). If these all stacked up, then I would guess you wouldnt achieve beyond friendly but that's just a stab in the dark without knowing all the elements of the game!