Can't access some websites

Good evening,

For some time, it is impossible for me to access some websites, from a macOS or from a linux.
The reasons seem diverse but I am sure there is a common problem.
Each time the website appears for a fraction of a second, then an error message appears.

For example, on the website sadeya.com, the message is "thank you to come back a little later, sadeya is in maintenance ...", or even the site widrax.com which shows me "PHP Fatal error: Call to Undefined method mysqli_result ::...

Can't access some websites