I have tried on different devices but option doesn't work well unless you spam click add another option till finally moves you to a new page to make poll instead of the pop up that doesn't work
Thats is why I use my computer to make forum polls and report posts. Everything else on the mobile version of the forums works fine though except for creating polls and flagging posts.
It's a common bug with an easy fix.
Certain parts of the pop-ups may not fit on the screen correctly, show up properly, and be clicked on. I'm sure these bugs can be patched by reformatting the pop-ups user interface (UI) on the mobile forum website.