paes wrote: They install a new version of Plesk and change php mode from apache to FastCGI
It seems FastCGI has more restrictions than apache mode.
By default /var/lib/php/session owner is www-data (or apache) system user. With fcgi, you have to put fcgi in www-data group, change the owner of /var/lib/php/session or ... there are a lot of possibility
Assistance on LimeSurvey forum and LimeSurvey core development are on my free time.
I'm not a LimeSurvey GmbH member,
professional service on demand
(or search sondages pro).