This is being caused by an expired WSKey.
To find out if your key is expired, from the command line in your EZproxy folder, type the following: ezproxy -sd
EZproxy will attempt to validate the key:
Attempting to revalidate EZproxy license key with OCLC server. Key is unauthorized (ExampleKEY-5o1TZuDIXXXXXXXXX1234567890). Current license key expired on (example date) 2019-12-24 09:00:00.
How to update your WSKey.