Upgrade mysql version and unable to access admin

Hello everybody

I have trouble to reach admin area and after reading lots of posts here i didn’t found my answer.

Ok after watching Woocommerce report asking me to upgrade php and mysql versions, last night i start to upgrade them using whm

I had php 5.3 and mysql 5.4 and i upgraded to mysql to 5.6 first

Then i upgrade php to 5.6 but i had apparently some trouble with my client’s website so i decide to downgrade to previous php version (with a “save config” i made previously). Website seems to work, i had some error with few plugins but now i can login using woocommerce frontend form. All is nearly ok, users can login and buy products using woocommerce.

If i login ad admin (using the fronted form), i can see the upper black bar telling me that i am login correctly. But if i try to access admin area, wp bring me to wp-login.php and disconnect me. If i try to login using wp login, it reload the same page with no error message.

I tried numerous solutions provided by wordpress documentation or advices from users with no luck.

Do you think there is an issue with mysql upgrade or maybe my apache compilation? I am not very confortable with server configuration ??

Thank you guys