Error 500 on siecmi.com

Good day, in July my web page www.siecmi.com generate ''an error 500''.

First nota that i did not :
- go inside my wordpress website for 2 months (it was in May);
- keep desactivate the ''automatics updates'' from wordpress

And also:
- I never touch the httacces since many years

To solve this porblem i tried:
- replace the htacces from an old save from severals months ago
- desactivate and then delet my graphic theme
- desactivate all extensions
- i load some full save up to april and nothing change.

Today my OVH website i used since more 12 years old is still not working and it could be nice you can help me because there is no reason after all tries i did it still not working.

Thank you for your feedback
William