mautic.ERROR: CAMPAIGN: An exception occurred while executing 'SELECT

Your software
My Mautic version is: v3.1.2
My PHP version is: 7.3.23
My Database type and version is: 5.7.32

Your problem
My problem is: campaigns don’t run with the error below
These errors are showing in the log:
mautic.ERROR: CAMPAIGN: An exception occurred while executing ‘SELECT AS id_1, AS name_2, t0.description AS description_3, t0.type AS type_4, t0.event_type AS event_type_5, t0.event_order AS event_order_6, AS properties_7, t0.trigger_date AS trigger_date_8, t0.trigger_interval AS trigger_interval_9, t0.trigger_interval_unit AS trigger_interval_unit_10, t0.trigger_hour AS trigger_hour_11, t0.trigger_restricted_start_hour AS trigger_restricted_start_hour_12, t0.trigger_restricted_stop_hour AS trigger_restricted_stop_hour_13, t0.trigger_restricted_dow AS trigger_restricted_dow_14, t0.trigger_mode AS trigger_mode_15, t0.decision_path AS decision_path_16, t0.temp_id AS temp_id_17, AS channel_18, t0.channel_id AS channel_id_19, t0.campaign_id AS campaign_id_20, t0.parent_id AS parent_id_21 FROM campaign_events t0 WHERE (t0.parent_id IS NULL AND t0.campaign_id = ?) ORDER BY t0.event_order ASC’ with params [18]: SQLSTATE[HY000]: General error: 2006 MySQL server has gone away

Steps I have tried to fix the problem: nothing