If you applied SO00888, which is the PTF for Web Services INC12, your UI version will be 18.0.1.201803261455, if you applied all the April maintenance, you might get a newer UI version.
If you are still experiencing issue with the package approval action, please open CA ticket and enter the information such as mainframe Endevor and Web Services version, the UI version, the screenshot of the package approval action on the Eclipse (showing the approval button grey out), and the complete SYSOUT of the Tomcat and spawn task log.
I will try to replicate the issue in house and will raise that to L2 if there is issue with the UI version 18.0.1.201804041328 regarding the package approval. my test system which is on 18.0.1.201803261455 has no problem with the package approval. Joe Gorel from Optum also installed 18.0.1.201803261455 and he is not experiencing your issue. RBS installed all April maintenance last week, so far no reports of the package approval issue.