Hi There,
I changed the PHP version to 7.0 and the cornerstone is working fine now.
I also updated this code in your wp-config.php
file:
define('AUTH_KEY', 'ba}hkcTf#ttR&|0wOt#XPKH+@%_FDvX}UIRgv]+ElXPX)?2?tP@Fl6qh%J5}p!mK');
define('SECURE_AUTH_KEY', ',}e<P]~6jl~rItqL@a{T8c/$9%~Q|)qa57JSy9E=h|fGP%u);P7,TnS+I+gD$QWt');
define('LOGGED_IN_KEY', 'lJ6V5IQr_z436:l]!Esab-3,WV<]y|rde]R=-E+|gii)cZawVy69M|kQ~,WX5>>D');
define('NONCE_KEY', 'E6r CY+ {hCvpKXbA<+kF^JCYw$xdZ{j6-w_XERObWJ~zH_+@E8qsh2~?aar^BvV');
define('AUTH_SALT', 'drlcM> WVFoG%*E^T^+!620a$m6)]uuG5uxg>;$k-;gRTj(nDuUS/+*p%oOK|+ 3');
define('SECURE_AUTH_SALT', 'N909cm`xE(fCrr}/~kR+Yipmrqt6KgN!}7`{ei Es{5Cb|SQYPxMBE7*Q$W1/Vmy');
define('LOGGED_IN_SALT', 'E|*C}CgK3{2H,T,4ct{Nj4T&VnJI1/N]}L9E2alWD|*Y%e++j|YYX-Zezo?zoC-r');
define('NONCE_SALT', '&#%!W3O9!Ce%RN&Sk0g&[_$9+*1RnJKnuI8QU4~h&AaQ>w`VPz=k&7~H0+2lt-c%');
Regards!