I'm searching for an answer to a similar question and noticed yours hasn't had any responses yet. It helps if you add "Tags" at the bottom of your query, choosing existing tags that are similar to your problem. Then more people with better expertise seem to "find" your query. Unfortunately I have no idea why your keyboards don't show but it must be something simple. I assume you're using FMGo13 on the iPad as well as FMP13 on your desktop?
My problem is that while I can get the keyboards to appear most times, I can't get it on drop-down lists. So if I have a text field using a drop-down list control style, I get a blank and then have to tap the "list" icon to get the keyboard.
So if you get a response by re-sending your query with tags, maybe I will also.
Happy New Year,