Encontrei uma resposta aqui
1. Go to Tools > Preferences.
2. Make sure that Allow only one instance under
Instances is unchecked.
3. Choose All at the bottom-left corner,
under "Show Settings".
4. Make sure that Allow only one running instance under
"Performance options" is unchecked.
5. Make sure that One instance when started from file
under "Performance options" is unchecked.