You need to update App.json because in version 15 we need to tell base application in dependencies.
Sample app.json:
{
"id": "xxxxxxxxxxxxxxxx",
"name": "xxxxxxxxxxxxxx",
"publisher": "xxxxx",
"version": "1.0.0.15",
"brief": "",
"description": "",
"privacyStatement": "",
"EULA": "",
"help": "",
"url": "",
"logo": "",
"dependencies": [
{
"appId": "63ca2fa4-4f03-4f2b-a480-172fef340d3f",
"publisher": "Microsoft",
"name": "System Application",
"version": "1.0.0.0"
},
{
"appId": "437dbf0e-84ff-417a-965d-ed2bb9650972",
"publisher": "Microsoft",
"name": "Base Application",
"version": "15.0.0.0"
}
],
"screenshots": [],
"platform": "15.0.0.0",
"idRanges": [
{
"from": 55500,
"to": 55550
}
],
"contextSensitiveHelpUrl": "Contracts.com/.../",
"showMyCode": false,
"runtime": "4.0"
}
