Text Flow has Ceased Operating

[Jack]

After typing away on an existing document containing page masters wotj text flow enabled, suddenly, fo no apparent reason, that feature has gone away, and a red 'oberflow' box appears near the lwer right corner of the page. I vewed oextras | show text threads, and they do not appear. So apparently, inadvertantly, I disabled the text threading. If one of you would please show me how to re-enable txt threads, I would be greatful.

[Jack]

Since my original post, I have tried restarting inDesign, restarting my iMac and openiong a duplicate, 8-day-old copy of the same document, into which I pasted content from 'Document 1' [in original post] with 'paste and match style', one page at a time, until the last page, when the same problem reappeared.

So now, I'm somewhat at a loss. Unless I hear from one of you in the next 60-90 minutes, I intend to uninstall and reinstall inDesign.

[Geоrge]

Can you show screenshots of what you do and what you need? 

What I understand now - you are try to insert many pages of text into master page. This is nonsense. You're need to insert text into frames on pages. 

https://youtu.be/STxQ62cYgWI