Walls won't connect despite walls tag when exported

I have used the walls and tags in my other mods but despite the tag element being identical to my old mod which has the walls connect fine, when I export the mod, the wall blocks will not connect to each other even though in the test environment the feature works fine? My old mod is able to export and have the walls connect but my new one isn't? the tag registry name is walls, tag namespace minecraft and the tag type being blocks and wall the elements are under the tag? Is anyone able to help?