After reading your question, what you are describing is a blockage in one of the transmission return lines. The return lines route the transmission fluid through the transmission intercooler before it begins its trip back through the tranny.
Since there’s only one line open, flow through the transmission has been cut by more than 50 percent as there are probably buildups within the transmission that take any flow and cut it further. So, since the flow is weak already and lack of the secondary return line is keeping the transmission from working at all.
That’s why you are not having any sort of PRNDL action when you go through the gears.
To fix this, you will have to unhook the slack hose and look at it closely. Is there a buildup in the connector? Has the connector been pinched or damaged by being dropped on the ground or, perhaps, crushed underneath a boot accidentally as you worked on the transmission? If the connector seems okay and clear, I would take a piece of hard-drawn copper wire — you can find it in some old TV cable — cut a length and then snake it down the connector to see if there might now be a buildup of deposits at or near the hose endpoint. Sometimes, a slight buildup near the end of a hose encourages further buildup and can pinch things off until there’s no flow.
If everything on the hose side looks good, take a close look at the connector into which the hose slips. It is possible that when you pulled the hose piece out of the connector that something might have distorted or pinched off in the connector itself. If this is the case, you will have to replace the connector so your transmission has fluid flow again. Without strong fluid flow, even though the transmission has been repaired and placed back in the housing, there will be no flow and no gearing as well.
Check the connections and I think you will find buildups or damage on either side. If this is the case, then you will have to swap out the hose return line, the connector or the line feeding the connector, as well. Let me know via a comment if there is anything else I can help you with relating to this repair.