TV connected to laptop via HDMI but still no signal?

Moin, I connected my laptop (HP, Windows 10, 20H2) to the TV (Sharp) via HDMI. The TV shows "No Signal". The television is recognized as a second monitor on the laptop itself. I've already done the following things:

Checks whether the TV is recognized in the display settings of Windows and also controlled, it is (is set to duplicate display).
Searched for Windows updates and installed
PC restarted (multiple times)
Another HDMI device (FireTV Stick) connected to the TV - is recognized
Driver updated
In the NVIDA control panel, the PhysX setting of select automatically switched to both the graphics card and the CPU
Cable checked several times

Does anyone here have any idea what might be the cause? I don't have a second HDMI port on my laptop, nor a display port or VGA.

You restarted the PC with the monitor connected so that Windows would recognize the television when it booted?