Have you tried placing the text while holding the shift key on your keyboard?
A reader suggests that I should try holding down the shift key when placing...
That does indeed change the cursor, however doing so adds an ENTIRELY NEW set of frames throughout the publication, on top of the ones that are already in the layout... :~(
When I position my cursor near the edge of the first, already drawn, frame; it changes aspect from a 'corner' with lines representing text to 'a pair of brackets/paratheses' with the lines in the middle indicating that the text will be placed there instead of creating a new frame. Also if the first frame is selected before clicking on File>Place>...>Open the text is placed automatically in that first frame.
Yes... You describe the way it USED to work. My next move will be to either reinstall, or delete prefs, etc. I just thought that it would be a good idea to see if something was changed in 2017 that I have missed in the announcement. Clearly, my copy is damaged somehow...
Two things to look for:
1. Open your Layers panel and spin open the layer. This will show you the objects on the spread. One possibility is that there are already too many frames.
2. Show Text Threads and click on the first frame. Are the other frames linked? Do they stay linked as you work?
Also, reading through your steps, a couple of things jump out.
1. Skip step 2. Click an insertion point anywhere in your threaded text and export it to tagged text. It will get all the text in the threaded frames.
2. Skip double-clicking the in port or the out port, as that will break the link to the threaded frames.
3. Confirm that your frames are still threaded. Click an insertion point and place the edited tagged text. It will flow into the threaded frames.
4. The empty port means it is no longer threaded. Best practice: don't unthread. Don't double-click a port.
If you do unthread the frames and see an empty port, you need to re-thread those frames.
Let me know if this helps!
Thank you to everyone who offered solutions. A solution has presented itself...
Is it possible that the document itself was damaged such that it would alter the behavior of text composition tools? Because, I took the first troubleshooting step: Start with a new document...
Create a NEW document, place the tagged text, collapse that thread into a frame on the pasteboard, re-place the tagged text, link to an existing frame, and -- text flow through linked frames working as expected... A puzzle, but one I'm happy to live with!