You are lucky. It seems that they have changed their mind and now block paying Go users from exporting other than PNG files. Pretty unkind and unprofessional! But they got their money from me under false advertising! What can I say. They answer to my emails only in obscurity, even after I showed them my receipt of payment of $119 per year. I feel abused. But they can do what they like I guess. So Sketchup Go is totally useless to me now. And $119 taken for nothing!
But there was no trial version to actually find out of the export function worked. They obviously either took it off to get you pay for a higher version, or let some have it and some not. I have worked with many other programs on my Mac.
It works fine for the rest of us, so instead of ranting about it why not try to figure out what the problem is? When you go to export under the upper left three lines menu what options do you see? Can you post a screen shot like this one below showing what your menu looks like? Hopefully your 25 years of 3D experience will help you do that.
That iPad interface for choosing the export option is not the most obvious way to do it. Touch where it says Image (png), and scroll the list. There are eight formats you can export, one of which is Object File (.obj).