For ionic 4, you must change the "version" field in the "widget" field (usually line 2) in the config.xml file.
For instance:
<widget id="myapp.mycompany.com" version="0.0.3" xmlns="http://www.w3.org/ns/widgets" xmlns:cdv="http://cordova.apache.org/ns/1.0">
In this case, just change the version from 0.0.3 to 0.0.4 or to any other number.
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