I have had trouble with getting buttons of any kind to work in portals with Web Direct in FMPA15.
When this happens my only solution is to create a new portal and delete the old one. this usually will get the buttons working. I have figured out the buttons themselves are not the issue but the portals are. I can copy all the buttons from the non functioning portal and the work in the new portal.
As well if I remove the buttons from the portal they work just fine. They are sized within the portal row. and nothing changes except the portal object instance. Is this a known problem? I know there were some issues with buttons in portals and web direct a while ago but I thought they were all fixed.