no click on retreat button

sorry to say the click on retreat button still does not work.
the change to " disabling visual themes " work around does not do it.
I suspect anything to cause update of screen will help.
I had this same problem with GBS battle screen and turning full screen option off & on helped.

If this is to do with the campaign, and the inoperable retreat button that can appear. i may have an answer. i noticed this happening to me in the campaign, and after about the 4th time realised it happend when i attacked a planet that at the same time attacked the planet i deployed the fleet from.

hope this helps.

The other reason is when you have nowhere to retreat to (for example, the defending planet is cut off from friendly planets)

Yes this is correct. sometimes you are ‘cut-off’ and surrounded and just cannot retreat to a connected planet.