[Edit: I see you found the problem while I was typing]
Does the front passenger door window switch work? If so then it's not the relay. It's the only switch separately powered other than through the driver door switch pod. If the RF switch also doesn't work and given that the fuse is okay (spin it a little) then the relay is suspect (know the wire colors when searching under the dash to verify the correct relay). If the RF switch works and no others do then it's almost guaranteed a broken (red) wire at the driver door hinge, the most common power window failure problem. The second most common is pitted dirty contacts in the bottom of the window switches that act up individually. If you mend a broken hinge wire (crimp sleeves are appropriate here rather than solder due to heat affecting copper strand strength), try to feed the splice into the pillar a bit so that fresh wire is doing the bending. Adding a small length of wire further back may be needed to gain the needed length. The reason I don't recommend splicing in a section of wire at the break is because auto store run wire is often of poorer quality than the Volvo harness so may fatigue and break again sooner.

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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now