It was happen to me, too, in a device I replaced screen.
Pocketbook Touch Lux 4 was manufactured with at least two LCD panels: ED060XH7 and EX060XCD. The latter (and probably later) have touch sensor glued on top of the screen, previous have the sensor secured under thin glass layer. These panels are electrically and mechanically fully compatible, so it's possible to replace each with the other. As ED060XCD is almost unavailable to buy, I replaced it with ED060XH7. It was working OK, I glued everything happy, and performed firmware upgrade - the touch failed exactly as yours.
After some deeper digging, replacing touch chip, connecting console to two pocketbooks with different panels, I noticed difference in settings for the panels in Pocketbook Linux firmware: console command /bin/hwconfig shows
- device_touchpanel=8 for PB manufactured with ED060XH7
- device_touchpanel=16 for EX060XCD
I don't know how to change this setting.
I noticed that firmware upgrade process stores initial settings in touch panel chip, so it's the reason for the failure after upgrade. The upgrade probably uses device_touchpanel to determine values to store.
HOW TO FIX your PB with no tools:
You have to connect the touch panel connector (only) to another pocketbook which have proper setting to your panel and force firmware upgrade on the pocketbook. The correct data will be saved in touch chip. This can be done relatively easy, only with opening rear cover of the both pocketbooks. To force firmware upgrade save the firmware on SD card, insert it to pocketbook at switch it on holding both "next" and "previous" physical buttons.
The touch panel type is printed on screen (largest) connector of the panel (you will have to disconnect it to check), the touch connector is on the opposite side.
If it's working, disable firmware upgrade, as it can break it in future.