Appointments+ crashed website

Hello,
I've set up the hours for all the workers (plugin worked fine before), and have tried to
select service>select worker for second worker on front end. All of a sudden, the website crashed with a 500 server error. I wasn't able to access it until I renamed the Appointment+ directory to inactivate the plugin. If I try to activate it again, entire site goes down. Could you please take a look? (heads up, this is live site) You already have access to this website, let me know if you need ftp access too. Thanks!

Error log:
[Mon Apr 03 13:02:17 2017] [error] PHP Warning: array_key_exists(): The first argument should be either a string or an integer in /home/.../public_html/wp-includes/cache.php on line 725, referer: http://physicalblissmarin.com/wp-admin/post.php?post=61&action=edit
[Mon Apr 03 13:00:57 2017] [error] PHP Warning: array_key_exists(): The first argument should be either a string or an integer in /home/.../public_html/wp-includes/cache.php on line 725, referer: http://physicalblissmarin.com/wp-admin/edit.php?post_type=page
[Mon Apr 03 08:47:51 2017] [error] PHP Warning: array_key_exists(): The first argument should be either a string or an integer in /home/.../public_html/wp-includes/cache.php on line 725, referer: http://physicalblissmarin.com/book-an-appointment/
[Mon Apr 03 08:44:18 2017] [error] PHP Warning: array_key_exists(): The first argument should be either a string or an integer in /home/.../public_html/wp-includes/cache.php on line 725
[Mon Apr 03 08:44:01 2017] [error] PHP Warning: array_key_exists(): The first argument should be either a string or an integer in /home/.../public_html/wp-includes/cache.php on line 725, referer: http://physicalblissmarin.com/wp-admin/edit.php?post_type=page
(paths etc edited for privacy)