KW88 black screen but I hear the sound of watch booting

My KW88 was functioning OK with KW88-CS1-B-GSM-PHT-20171111 but I tryed to flash KW88_CS1_OHH_B_GSM_PHT_20180821 to see if there was some improvements, specially the battery lasting more time.
Tryed first with Download only (not really, had to do Format + Download because of error that states I had to do a format) and then also with Firmware upgrade.
Both flash OK, in both the clock starts but screen remains black (it gives a 1 second flash of light and I hear the sound of clock starting but nothing more on screen, just black).
Is this normal behavior, do anyone have some idea how to recover? Firmware KW88_CS1_OHH_B_GSM_PHT_20180821 is just to correct the inverted screen problem? It has no other improvements?
I can flash back to KW88-CS1-B-GSM-PHT-20171111 and clock starts and work fine but I was hopping to install a newer (and better!) firmware.
Thanks in advance for all enlightment anyone could offer.

nunodmcosta

so many had done the same mistake you have done, it wo’nt be easy to fix the issue as you need to know which firmware was on the watch and which type of screen you have.

pablo11

The correct firmware is available but as you used format all + download you will not have any IMEI number or WiFi / BT MAC addresses.

It failed at download only for a very good reason.
When this happens you should stop.
Forcing it ends badly…

Hi there pablo11 and soniasophie9697.
I can flash back to KW88-CS1-B-GSM-PHT-20171111 with success and the watch starts and works fine (that was the firmware in the watch prior to flash KW88_CS1_OHH_B_GSM_PHT_20180821).
The screen type sould be the first screen type that was release with KW88, since I bought the watch about 2 years ago.
My curiosity: the letters PHT, OHH, NHH in the firmware name refers to the screen type?
And firmware KW88_CS1_OHH_B_GSM_PHT_20180821 is just to correct the inverted screen problem or has it other improvements?