The bolt is powered by the tiny spring, check to see if it's in place. The screw in the bolt should be tight, but not to the point where you risk breaking it.
The bolt is activated by the rebound lever. Unless the pin at the rear that holds it in the frame is out of place, simply installing a new main spring shouldn't have affected bolt function.
Make sure the front of the rebound is properly in place under the hand. Often during disassembly the hand slips outward and the rebound slips off the ledge in the slot on the back of the hand. The rebound and thus the bolt will not operate correctly.
To check bolt function with the side plate off, put a finger on the hand to prevent it from slipping outward and out of place.
With the side plate in place just look up inside the frame as you operate the hammer.
In either case, the instant the hammer starts to move back the bolt should begin to drop.
You can view the operation of the bolt "tail" as the tiny triangle surface pushes the tail upward, which caused the front of the bolt to drop into the frame.
This should allow you see WHY the bolt isn't operating, which will likely be something out of place which is preventing the tail of the bolt to be engaged by the rebound.
When the hammer is cocked far enough, the bolt tail will slip off the rebound with a clean "click".
When the hammer is lowered again, the tail of the bolt should snap back onto the triangular surface on the rebound.
If something is out of place or "whatever", the tail of the bolt will not snap back onto the rebound, and the action will operate without operating the bolt.