Are you reproducing the reaction exactly, or are you doing a variation? If the yield is only 3%; what happens to the rest of it? Do you see a lot of "tarring"? Have you tried adding a spatula of catalyst after eg. 3 hrs? Perhaps you can try to substitute (PPh)4Pd as catalyst; that's generally more efficient.

There are apparently a lot of ways to make benzofurans, Personally, I hadn't seen this decarboxylative method before; perhaps some other procedure is more reliable? You may find some alternative routes here: http://www.organic-chemistry.org/synthesis/heterocycles/furans/benzo[b]furans.shtm

The method reported will be extremely sensitive to electronic factors. Both the electron poor alkyne and the aldehyde adjacent to the iodine in their substrate act strongly in favour of product formation.

Mechanistically the reaction most likely occurs via a Michael type addition to the alkyne followed by an intramolecular Heck reaction.

As suggested above, tetrakis is worth trying, potentially you could also change metals to something more alkynophilic such as a Au(I) catalyst. A catalytic quantity of CuI or a silver salt can aid the oxidative addition across the Aryl-Iodide bond.