Since Google is retiring the panoramio service, is worth to look at the new platform Google Maps View. Of course you are required to create a Google account but that is fairly simple process. I did not manage to upload a photo sphere successfully straight away so I summarize the steps here.
It is not enough to create a equirectangular image and upload as photo under the +.
A panoramic image has to deliver specific Photo Sphere XMP Metadata in order to be recognized by Google as a Photo Sphere. You can either do it manually by tinkering the Exif info of the file with a tool like ExifTool or use the easier way by using this Google App. This is a detour which is not straight forward (unlike other Google tools), I guess they will migrate this feature into the upload process sooner or later.
After this step your photo sphere has not yet been put up for Google Maps. The app only adds the basic meta data to your image. Click on the download to get back the image file. You have to download this image and add the image. Now it will be recognized as photo sphere and properly rendered. Note, it takes a while before it actually pops up on Google Maps (not only in your profile).