Custom Dropdown field broken

I created a custom dropdown field and it doesn’t show up. I’ve followed the troubleshooting steps on this page by deactivating all plugins except Ultimate Member and switching to the Twenty Fifteen Theme, but I’m still experiencing this error. What PHP extensions are required for this plugin to work? I’m running CentOS with the following install info:

### Begin Install Info ###

## Please include this information when posting support requests ##

--- Site Info ---

Site URL:					https://readinquirewrite.umich.edu
Home URL:					https://readinquirewrite.umich.edu
Multisite:					No

--- Hosting Provider ---

Host:						DBH: localhost, SRV: _

--- User Browser ---

Platform:                 Apple 
Browser Name:             Chrome  
Browser Version:          67.0.3396.99 
User Agent String:        Mozilla/5.0 (Macintosh; Intel Ma 
			  c OS X 10_13_4) AppleWebKit/537.
                          36 (KHTML, like Gecko) Chrome/67
                          .0.3396.99 Safari/537.36
                          
---- Current User Details --

Role: administrator, um_admin

--- WordPress Configurations ---

Version:						4.9.6
Language:					en_US
Permalink Structure:			/%year%/%monthnum%/%day%/%postname%/
Active Theme:				Twenty Fifteen 2.0
Page On Front:				Home (#50)
Page For Posts:				 (#0)
ABSPATH:					/usr/local/miserver/read-inquire-write/
All Posts/Pages:				4
WP Remote Post:           		wp_remote_post() works
WP_DEBUG:                 			Disabled
WP Table Prefix:          			Length: 3, Status: Acceptable
Memory Limit:   				40MB

--- UM Configurations ---

Version:						2.0.17
Upgraded From:            		None
Current URL Method:			HTTP_HOST
Cache User Profile:			No
Generate Slugs on Directories:	Yes
Rewrite Rules: 				Yes
Force UTF-8 Encoding: 		No
JS/CSS Compression: 			No
Nav Menu Settings: 			Yes
Port Forwarding in URL: 		No
Exclude CSS/JS on Home: 		No

--- UM Pages Configuration ---

User:						https://readinquirewrite.umich.edu/user/
Account:						https://readinquirewrite.umich.edu/account/
Members:					https://readinquirewrite.umich.edu/members/
Register:						https://readinquirewrite.umich.edu/register/
Login:						https://readinquirewrite.umich.edu/login/
Logout:						https://readinquirewrite.umich.edu/logout/
Password Reset:				https://readinquirewrite.umich.edu/password-reset/

--- UM Users Configuration ---

Default New User Role: 		0
Profile Permalink Base:		user_login
User Display Name:			full_name
Force Name to Uppercase:		Yes
Redirect author to profile: 		Yes
Enable Members Directory:	No
Use Gravatars: 				No
Require a strong password: 	Off
Editable primary email field in profile view:	Off

--- UM Access Configuration ---

Global Site Access:						Site accessible to Logged In Users
Custom Redirect URL:						
Exclude the following URLs:				
Backend Login Screen for Guests:			No
Redirect to alternative login page:			https://readinquirewrite.umich.edu/login/
Backend Register Screen for Guests:		No
Redirect to alternative register page:		https://readinquirewrite.umich.edu
Access Control widget for Admins only: 		Yes
Enable the Reset Password Limit:			Yes
Reset Password Limit: 3Disable Reset Password Limit for Admins: No
Blacklist Words: 							5

--- UM Email Configurations ---

Mail appears from:  			Read.Inquire.Write
Mail appears from address:  	[email protected]
Use HTML for E-mails:   		Yes
Account Welcome Email:  		Yes
Account Activation Email:   	Yes
Pending Review Email:   		Yes
Account Approved Email: 		Yes
Account Rejected Email: 		Yes
Account Deactivated Email:  	Yes
Account Deleted Email:  		Yes
Password Reset Email:   		Yes
Password Changed Email: 		Yes

--- UM Total Users ---

                All Users(17)
administrator(4)
subscriber(13)
um_member(12)
um_admin(4)
none(0)

--- UM Roles ---

                Administrator (administrator)
Editor (editor)
Author (author)
Contributor (contributor)
Subscriber (subscriber)
Member (um_member)
Admin (um_admin)

--- UM Custom Templates ---

                N/A

--- UM Email HTML Templates ---

                N/A

--- Web Server Configurations ---

PHP Version:              			7.2.6
MySQL Version:            			5.5.56
Web Server Info:          			nginx/1.12.2

--- PHP Configurations ---

PHP Memory Limit:         			256M
PHP Upload Max Size:      			2M
PHP Post Max Size:        			8M
PHP Upload Max Filesize:  			2M
PHP Time Limit:           			30
PHP Max Input Vars:       			1000
PHP Arg Separator:        			&
PHP Allow URL File Open:  			Yes

--- Web Server Extensions/Modules ---

DISPLAY ERRORS:           			N/A
FSOCKOPEN:                			Your server supports fsockopen.
cURL:                     			Your server supports cURL.
SOAP Client:              			Your server does not have the SOAP Client enabled.
SUHOSIN:                  			Your server does not have SUHOSIN installed.
GD Library:               			PHP GD library is NOT installed on your web server.
Mail:                     			PHP mail function exist on your web server.

--- Session Configurations ---

Session:                  			Enabled
Session Name:             			PHPSESSID
Cookie Path:              			/
Save Path:                			/var/lib/php/session
Use Cookies:              			On
Use Only Cookies:         			On

--- WordPress Active Plugins ---

                Ultimate Member: 2.0.17

### End Install Info ###