Help My Endnote X8 will not open on sierra anymore

my endnote X8 won’t open on sierra. I keeo getting a message that say my endnote is being used by someone else an dI should try again later.

It is however not being used by anyone else other than me. I had it downloaded on various macs in order to sync it while I’m on the road. However none of the Versions work even though they had worked perfectly before.

Plsss Helppppp !!!