First, confirm that your shortcode looks something like the following:
[menu_in_post_menu menu=3 style="dropdown" placeholder_text="Choose a topic..."]
Where the “menu=” number is the ID of your chosen menu as created by the Menu In Post Tools, and the placeholder_text is in double quotes.
The other thing I notice is that there is a recurring error in the HTML for the menu on your page. Every item has the “selected” attribute set to “selected.” None should be selected, allowing the placeholder to be the visible option. Since they’re all selected, it’s not surprising that you’re getting some weird, random results.
Here’s the relevant HTML from your page showing all the options are selected:
<option value="#">Choose a topic</option>
<option value="https://test.mggno.com/resources-2/#agcenter" selected="selected">AgCenter Publications</option>
<option value="https://test.mggno.com/resources-2/#Dan-Gill" selected="selected">Dan Gill</option>
<option value="https://test.mggno.com/resources-2/#facebook" selected="selected">Facebook Pages to Follow</option>
<option value="https://test.mggno.com/resources-2/#GNO-Gardening" selected="selected">GNO Gardening</option>
<option value="https://test.mggno.com/resources-2/#Google-Search-Tips" selected="selected">Google Search Tips</option>
<option value="https://test.mggno.com/resources-2/#master-gardener-favorites" selected="selected">Master Gardener Favorites</option>
<option value="https://test.mggno.com/resources-2/#plant-societies" selected="selected">Plant Societies</option>
<option value="https://test.mggno.com/resources-2/#inspiration" selected="selected">Sites for Inspiration</option>
<option value="https://test.mggno.com/resources-2/#superplants" selected="selected">Superplants</option>
<option value="https://test.mggno.com/resources-2/#youtube" selected="selected">YouTube Channels</option>
I see that you’re using Elementor, which may be causing a conflict with the Menu In Post plugin, or some other plugin you’re running that handles menus could be the culprit.
It also looks like you have the menu in a widget instead of in a post. If you’ve got it in a widget, I’d probably try moving it to the post and see if it fixes the problem before I did anything with Elementor.
Since I’m guessing you want to keep Elementor even if it is causing the conflict, you could try the WordPress Menu Block instead of Menu In Post to see if it plays more nicely with Elementor than Menu In Post.
Let me know what you figure out.