Hi @sergio83100 ,
unfortunately your change does not appear on my screen ... Correctly formatted it should look like this
Post #1 without code tags:
Hello,
I'm developing an application based on Spotspear's 1.44-inch keychain board.
The device is battery-powered, so deep sleep is required!
Everything works correctly, including the display addressing and the processor's deep sleep procedure.
However, I can't put the display really into sleep mode using the "enableDisplay()" method of the Arduino_ST7735 library.
It turns out that using this method is ineffective regarding the backlight. The screen goes blank, but the backlight stays on.
It should be noted that on this board, the display's BackLight is physically wired to 3.3V.
Should I note that this method doesn't affect the backlight?
Thanks in advance for your help...
End of post #1
I found older posts with a similar topic, e.g.
https://forum.arduino.cc/t/1-8-tft-st7735-backlight-control/562804/14
and
https://github.com/Bodmer/TFT_eSPI/discussions/998
So it is a generally known issue ... if one searches for it ... 
The backlight has to be controlled separately ...
I guess you are using the Adafruit library? If yes, you might also check the function enableSleep() instead of enableDisplay():
Good luck!
ec2021