Here is the solution. Pray that you have a copy of 5.3.0 handy. Delete 5.4.0 and then install 5.3.0. Problem solved.
Here is the error in the log:
Fri Aug 24 10:21:34 CDT 2018:ERROR:java.lang.IndexOutOfBoundsException: Index: 1, Size: 1
java.lang.IndexOutOfBoundsException: Index: 1, Size: 1
at java.util.ArrayList.rangeCheck(Unknown Source)
at java.util.ArrayList.get(Unknown Source)
at com.eviware.soapui.impl.rest.support.RestRequestParamsPropertyHolder.getPropertyAt(RestRequestParamsPropertyHolder.java:208)
at com.eviware.soapui.impl.rest.support.RestUtils.makeMatrixParameterString(RestUtils.java:242)
at com.eviware.soapui.impl.rest.support.RestUtils.makeSuffixParameterString(RestUtils.java:236)
at com.eviware.soapui.impl.rest.panels.request.ParametersField.<init>(ParametersField.java:65)
at com.eviware.soapui.impl.rest.panels.request.RestRequestDesktopPanel.initializeFields(RestRequestDesktopPanel.java:54)
at com.eviware.soapui.impl.support.panels.AbstractHttpRequestDesktopPanel.init(AbstractHttpRequestDesktopPanel.java:165)
at com.eviware.soapui.impl.rest.panels.request.RestRequestDesktopPanel.init(RestRequestDesktopPanel.java:62)
at com.eviware.soapui.impl.rest.panels.request.RestRequestDesktopPanel.init(RestRequestDesktopPanel.java:36)
at com.eviware.soapui.impl.support.panels.AbstractHttpRequestDesktopPanel.<init>(AbstractHttpRequestDesktopPanel.java:128)
at com.eviware.soapui.impl.support.panels.AbstractHttpXmlRequestDesktopPanel.<init>(AbstractHttpXmlRequestDesktopPanel.java:46)
at com.eviware.soapui.impl.rest.panels.request.AbstractRestRequestDesktopPanel.<init>(AbstractRestRequestDesktopPanel.java:61)
at com.eviware.soapui.impl.rest.panels.request.RestRequestDesktopPanel.<init>(RestRequestDesktopPanel.java:45)
