Text reflow not working

There's lots of reasons. 

Instead of posting videos you can attach the IDML file - in INDesign go to File>Export and choose IDML 

Then attach the file here - or a DM and we can take a look for you. 

It could be Keep Options

Line of text too long (like  URL with No Break) applied

It could be set to continue on Next Odd Page (you're trying to thread to Even Page)

And many othe reasons

You can view the text in the Story Editor 
CMD Y

or CTRL Y on PC

Then there should be a red line beside the text that is overset - might offer a clue to what's going on.