As soon as the update is done, the voice search must be enabled because it is disabled by default.

If the icon still does not appear, you have probably set a non-TTS voice.

The GPS signal has no influence with the voice search, and if you do not have an internet connection the icon appears equally and when you click on the voice search you receive the warning that this connection is missing.

In this year and a half I have always changed only the ux folder and the sys in the updates, using the default vr and vr_vde folders, and the voice search has always worked for me.
I wanted to try to change these two folders with the "new" ones that are in the last update, (with the vr folder that contains the 0419 and Lt-IL folders), but there was no difference.

Check your settings carefully, in fact the Skin should not affect with voice search.