Strange, it works for me and i have tested a lot with the latest version.

so pressing ctrl button and then hitting preview (it takes a little while) does not work?

Maybe this post helps as well?

https://helpcenter.websitex5.com/it/post/224663

Another option might be to download latest full version and install that one (from top right pulldown next to your name) -> download.

Then try again.

Page preview is not working this only first problem. Another problem is that all texts of all projects have been deleted, which probably causes the first problem.

The last time I worked with a Website was May 31st with version 2020.1.5. In the meantime, I upgraded twice to version 2020.2.4, with which I wanted to continue working today, June 30, but the above problems did not allow me to do so. That's why I deleted the new version and installed the old one (originally functional version 2020.1.5), but unfortunately this version also shows the same problems and I can't continue to build the website at all.
During June, my laptop was updated to WIN10, and since then (I assume) the problem with Website malfunction has started.

... so pressing ctrl button and then hitting preview (it takes a little while) does not work?

.... sorry, I try very much times, not work and all texts lost !!!

That's not very nice Marcel,

Works a  new project as it should? 

If so try to use the backup button in the project selection and see if there is an older working copy available.

If so export this project in step5.

then you have at least a save copy. try latest version and use a clean test project to see if all works as it should. If so import the previously exported project and cross your fingers....

TIP from https://helpcenter.websitex5.com/it/post/224663

Since the web preview seems to be related with a navigator client I changed the IP address of my computer, from DHCP to an static IP address, and BINGO, that made the change! I am back to see the web preview as usual. 

... but i don't know how to do it, how to set a fixed address? I have a microwave internet connection from a local (national provider) internet. PLDT Philippines.

... Reinstalling WIN10 to a previous version, I also do not know how to do it, sorry.

I have saved old projects, thankfully. But I have already performed your proposed procedure, but unfortunately with the same unsuccessful result. I exported the backed up project to the installed older version, but with the same result.
As I read the discussion you sent me, the problem is really related to the win10 updates, in my case to the update that took place between June 6-10.
So I don't know if I can uninstall those updates and how to do it?

I tried to uninstall some parts of the latest win10 update but it didn't help.
I don't know what to do now, because old backed up projects don't work and I can't even start a new project.
If I want a new project, the program will declare an error and close. He's been doing it for months, for months.

I had to create a new project by opening another functional project that I reworked.

I cannot work in this form (((

The same problem here:

https://helpcenter.websitex5.com/it/post/229756

The user has resolved by temporarily disabling the antivirus. The problem was the antivirus

Avast - i am not a big fan, not even a small fan.  It has only 1 advantage it's free.