First, sorry for my english. I'm italian.
I have a Realm that has switched from version 1.8.9 to 1.9 few days ago.
After the update, I went into the End Dimension with the intention of reviving the Ender Dragon that I've been destroyed in version 1.8., through the four crystals placed on exit portal.
But the Dragon has not appeared.
After this, I have reset the End Dimension in the following manner:

1) I have downloaded the last Realm backup on my PC.

2) I've deleted on that file the content of directory DIM1, which contains the END.

3) I have re-updated the file in the Realm section "Reset", that permits a local world upload.

After this procedure the End Dimension has been restored, in fact when I went into End, the world was different and rebirthed (the crystals on towers have come back and they are again here), but the Ender Dragon HAS NO APPEARED!! So I have killed myself to exit the End because without Dragon the exit portal does not appear!
What is the problem? And what solution can be found for this problem ?
Thanks for the help!