The preview does not play in shotcut 19xxxx

Hi , version 18 play correctly , version 19 does not , i can move the cursor with the mouse , but clicking on the play button , or pressing the space bar has no effect.Other problem on the two versions, using Generator crashes the program when clicking ok , i can’t make a color template.
Linux Lite 4.4,ubuntu 18.04 based
Cpu=amd Phenom II X8 33000
16gb ram ddr3 1600
Gpu=Nvidia GTX 660

Did you download Shotcut version 19xxxx from this website: https://shotcut.org/download/ ?

Where did you get Shotcut from? Did you download it from here?
https://shotcut.org/download/

Yes i did

The developers and many others do not have these problems on Linux and never have. It is also the first time I have heard anyone report it. If you or another person does not debug it, then I suspect it will not work. After trying to play, look in View > Application Log for any errors reported. You can also save that and upload it here.
Maybe there is a problem with sound output on your system. I would not be surprised; audio on Linux has many options that can lead to pitfalls like incompatibilities. For example, JACK could be running in a manner that is incompatible with PulseAudio. Shotcut uses SDL2, by default, if you know what that means.

Actually , there was no sound on my track , but i will investigate in this direction , i am also planning to try it on Mint 19.3.Thanks for the answer

Even if there is no sound, it needs to be able to play silent sound. Sound output drives the playback in Shotcut.

Ok , i untick “use jack” and it plays now , also the color template is ok …very strange???

Yes, that is strange. Do you see GPU Effects (unstable) at the top of the Settings menu? What is Settings > Video Mode set to?

HD1080x30fps