This happens because DHIS 2 uses brackets in some of their URLs, and because Tomcat version 8.5 later has prohibited the use of brackets in URLs.
The DHIS 2 team is working on a change in the API syntax to avoid the use of brackets, and to encode all API request URLs.
A short-term fix is to configure Tomcat to allow for brackets through the
relaxedQueryChars connector attribute. Open the following file:
relaxedQueryChars="" to the HTTP connector element:
This will allow brackets in URLs and DHIS 2 will function as before.