Failed to upgrade an old Aggregate server on GAE

Dear All,

Trying to upgrade an aggregate server v1.7.1 following the guideline on https://docs.getodk.org/aggregate-upgrade/#need-for-upgrading. However, the installation process was not successful. The log is as the following:

Unable to update:
java.lang.RuntimeException: Fatal problem encountered during deployment. Please refer to the logs for more information.
	at com.google.appengine.tools.admin.AppVersionUpload.isServing(AppVersionUpload.java:1051)
	at com.google.appengine.tools.admin.AppVersionUpload.access$200(AppVersionUpload.java:43)
	at com.google.appengine.tools.admin.AppVersionUpload$2.call(AppVersionUpload.java:884)
	at com.google.appengine.tools.admin.AppVersionUpload$2.call(AppVersionUpload.java:881)
	at com.google.appengine.tools.admin.AppVersionUpload$3.call(AppVersionUpload.java:1188)
	at com.google.appengine.tools.admin.AppVersionUpload$3.call(AppVersionUpload.java:1185)
	at com.google.appengine.tools.admin.AppVersionUpload.retryWithBackoffOptional(AppVersionUpload.java:1213)
	at com.google.appengine.tools.admin.AppVersionUpload.retryWithBackoff(AppVersionUpload.java:1183)
	at com.google.appengine.tools.admin.AppVersionUpload.commit(AppVersionUpload.java:881)
	at com.google.appengine.tools.admin.AppVersionUpload.uploadFilesTransaction(AppVersionUpload.java:223)
	at com.google.appengine.tools.admin.AppVersionUpload.doUpload(AppVersionUpload.java:197)
	at com.google.appengine.tools.admin.AppAdminImpl.doUpdate(AppAdminImpl.java:580)
	at com.google.appengine.tools.admin.AppAdminImpl.update(AppAdminImpl.java:65)
	at com.google.appengine.tools.admin.AppCfg$UpdateAction.execute(AppCfg.java:1543)
	at com.google.appengine.tools.admin.AppCfg.executeAction(AppCfg.java:390)
	at com.google.appengine.tools.admin.AppCfg.<init>(AppCfg.java:213)
	at com.google.appengine.tools.admin.AppCfg.<init>(AppCfg.java:119)
	at com.google.appengine.tools.admin.AppCfg.main(AppCfg.java:115)
com.google.appengine.tools.admin.AdminException: Unable to update app: Fatal problem encountered during deployment. Please refer to the logs for more information.
	at com.google.appengine.tools.admin.AppAdminImpl.doUpdate(AppAdminImpl.java:586)
	at com.google.appengine.tools.admin.AppAdminImpl.update(AppAdminImpl.java:65)
	at com.google.appengine.tools.admin.AppCfg$UpdateAction.execute(AppCfg.java:1543)
	at com.google.appengine.tools.admin.AppCfg.executeAction(AppCfg.java:390)
	at com.google.appengine.tools.admin.AppCfg.<init>(AppCfg.java:213)
	at com.google.appengine.tools.admin.AppCfg.<init>(AppCfg.java:119)
	at com.google.appengine.tools.admin.AppCfg.main(AppCfg.java:115)
Caused by: java.lang.RuntimeException: Fatal problem encountered during deployment. Please refer to the logs for more information.
	at com.google.appengine.tools.admin.AppVersionUpload.isServing(AppVersionUpload.java:1051)
	at com.google.appengine.tools.admin.AppVersionUpload.access$200(AppVersionUpload.java:43)
	at com.google.appengine.tools.admin.AppVersionUpload$2.call(AppVersionUpload.java:884)
	at com.google.appengine.tools.admin.AppVersionUpload$2.call(AppVersionUpload.java:881)
	at com.google.appengine.tools.admin.AppVersionUpload$3.call(AppVersionUpload.java:1188)
	at com.google.appengine.tools.admin.AppVersionUpload$3.call(AppVersionUpload.java:1185)
	at com.google.appengine.tools.admin.AppVersionUpload.retryWithBackoffOptional(AppVersionUpload.java:1213)
	at com.google.appengine.tools.admin.AppVersionUpload.retryWithBackoff(AppVersionUpload.java:1183)
	at com.google.appengine.tools.admin.AppVersionUpload.commit(AppVersionUpload.java:881)
	at com.google.appengine.tools.admin.AppVersionUpload.uploadFilesTransaction(AppVersionUpload.java:223)
	at com.google.appengine.tools.admin.AppVersionUpload.doUpload(AppVersionUpload.java:197)
	at com.google.appengine.tools.admin.AppAdminImpl.doUpdate(AppAdminImpl.java:580)
	... 6 more

Thank you in advance,
Imran