Android programming: How to activate soft keyboard with real keyboard paired on tablet

My problem is with an app that has been written for me, running on a Samsung Tab A, where I cannot get the soft keyboard to pop up anywhere in the app.  A bluetooth barcode scanner is paired, and I also have the Android setting turned on that says "Show on-screen keyboard".   And if I go into the "Memo" app that came with the tablet--similar to WordPad--I can scan barcodes into it, or I can touch the screen and the soft keyboard pops up.  Same with Chrome...if I touch the bar where you key in the URL, it pops up the keyboard like it's supposed to--and I suppose I could scan data into that same line.

But in this app written for me, I can scan in data with no problem, but I can't get the soft keyboard to pop up.   The developer  blames it all on me, insisting there is nothing he can do.  He keeps saying that there is nothing in his code that would suppress the soft keyboard.  But he won't tell me whether there is anything that will "activate" the keyboard.

I'm not at all familiar with this C# code written for a Xamarin environment.  But one thing I'm wondering is this: On an Android device, if you touch a textbox, is the soft keyboard supposed to pop up by default--or do you have to include code to tell it to do so?  I'm wondering if maybe he is missing some code that will tell the program to pop up the keyboard.

I do understand that the Settings need to be set up right, as outlined above, but they are--as evidenced by programs such as Chrome and that Memo app allowing both scans and soft keyboard entry.  Any ideas what could be happening in my program that would keep the soft keyboard from popping up when I touch the textbox?  TIA