How can I put it back the ring to my Jetset?
Have you tried just pushing it in? If it doesn’t stay in try some super glue.
the material is too hard to squeeze the ring fit into the groove
Try putting the ring in the freezer for 30 minutes, then give it a shot while it’s cold. That should shrink it a bit and it may be enough to do it. You may have to force it. Also take the yoyo apart so you can apply good pressure against a table.
Only glue it as a last resort. If the ring is in there that tight its placement being changed could effect play.
Don’t use glue if it does not fit in all the way, it will hang out ruin it and cause wobble.