Struggling with changing out a light fixture in the dining room.

Two switches control the fixture and one was a dimmer. The directions for the new fixture say not to use a dimmer so I changed out the dimmer to a regular on/off switch.

From the ceiling there are 7 wires. Two sets of red/white/black and the copper ground.The original fixture was connected strangely. One set was capped off and not connected at all. The black ceiling wire was connected to both fixture wires.. . and the red/white from the ceiling were capped off together.

The directions for the new fixture say to put white ceiling to the ribbed fixture wire and the smooth wire to the black ceiling wire. No mention of what to do with the red wire.

So.. I've tried this and the original installation with both fixture wires connected to the black ceiling wire and no luck.

I'm a bit confused with the all the possible variables including the two switches.. the dimmer and the ceiling wires.

Hopefully, I have explained it well and any help is appreciated.

Thanks,

Sean

Are the switches in 1 box/location?
No 3 way?
I would remove the wall plate, and see which wires are connected to the switches. Both switches likely have a wire connected to 1 and jumpered to the 2nd, this should be a constant hot, what are the colors to the other terminal on both switches? Red and black? If so then maybe each switches same color at the ceiling, The light need one connection to neutral(white)conductor with ribs/ridges, and the hot red or black will connect to the smooth conductor.
Try with just a bulb and socket if you have no meter/tester, at the least test the light before hanging to be sure bulb is still good and switch on fixture is on.
The reason for no dimmer is because most flourescents aren't dimmable, I think aren't is a word, I know ain't ain't.

From the ceiling there are 7 wires. Two sets of red/white/black and the copper ground.The original fixture was connected strangely. One set was capped off and not connected at all. The black ceiling wire was connected to both fixture wires. ...and the red/white from the ceiling were capped off together.

The directions for the new fixture say to put white ceiling to the ribbed fixture wire and the smooth wire to the black ceiling wire. No mention of what to do with the red wire.

So..I've tried this and the original installation with both fixture wires connected to the black ceiling wire and no luck.Just put it back exactly how it was. You did not need to change anything at all.

This is why I feel there should be no instructions included with things like this. Many times they only serve to confuse things. Rarely is it as simple as black-to-black and white-to-white.

If the original light fixture was controlled by a dimmer switch and another switch then the dimmer was a 3 way controlled dimmer. You need to replace it with a 3 way switch and not an on/off switch.