Do you have a recent save? It isn't a big deal, but when you lowered the 4 pieces of equipment on chains, a skill book (also on a chain) was lowered near the start of that area (out of sight from where you were). If you can, you may want to reload and get that instead of whatever you picked.
The door should be open if you keep going up the ramp past where you lowered the chains. There isn't anything else to do there.
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