Exception calling 'theme_boost_union_before_session_start'

line 200 of /cache/classes/factory.php: call to core_cache\factory->create_definition()
line 190 of /cache/classes/cache.php: call to core_cache\factory->create_cache_from_definition()
line 2467 of /theme/boost_union/locallib.php: call to core_cache\cache::make()
line 862 of /theme/boost_union/lib.php: call to theme_boost_union_manipulate_hooks()
line 900 of /lib/setup.php: call to theme_boost_union_before_session_start()
line 747 of /mnt/efs/tenants/moodleconfigs/russell.poodll.com.php: call to require_once()
line 40 of /config.php: call to require_once()
line 28 of /mod/lesson/view.php: call to require_once()

Error

Setting up of redis session failed. Please notify the server administrator.

Debug info:
Error code: redissessionhandlerproblem

Stack trace:

line 224 of /lib/classes/session/redis.php: core\session\exception thrown
line 149 of /lib/classes/session/manager.php: call to core\session\redis->init()
line 136 of /lib/classes/session/manager.php: call to core\session\manager::start_session()
line 907 of /lib/setup.php: call to core\session\manager::start()
line 747 of /mnt/efs/tenants/moodleconfigs/russell.poodll.com.php: call to require_once()
line 40 of /config.php: call to require_once()
line 28 of /mod/lesson/view.php: call to require_once()