Reflux in pyridine (as reported) or in dioxane (using few drops of pyridine or sodium carbonate as catalyst) was not successful
You need to use a base catalyst atleast about 1 mole equivalent to the nicotinoyl chloride. Make sure the nicotinoyl chloride dissolves in the medium. If it is not dissolved the reaction may not go forward. Alternatively you can try using excess aromatic primary amine that helps to drive the reaction
First, be sure that nicotinoyl chloride (mostly provided as HCl salt) is completely soluble in the medium (You may try DMF), then use 1.5 moles of the amine and piperidine as a basic catalyst.
I think the reflux with pyridine is a good procedure , So you might review the following points to check the possible error:
1- Check the purity of Nicotinoyl chloride hydrochloride. Old or untrustworthy sources may contain a decomposed nicotinoyl chloride.
2- You need to use Dry and pure pyridine so try to purify pyridine through distillation.
3- Perform the reaction under nitrogen.
1. Be sure of the dry solvents in use.
2. If it didn't work Try the acylation using Nicotinic acid and DCHCD in Chloroform.