Error:failed to launch instance "Win7": * Try again later [Error:no valid host was found.].

1. First see if all services have been started

Execute # nova-manage Service list

Binary          Host Zone Status State updated_at

nova - Consoleauth  mycontroller internal   enabled        :-)        2014 - 06 - 06 02 : 44 : 41

nova - scheduler    Mycontroller internal   enabled        :-)        2014 - 06 - 06 02 : 44 : 41

nova - Conductor    mycontroller internal   enabled       :-)        2014 - 06 Span class= "pun" >- 06 02 : 44 : 37

nova - cert         Mycontroller internal   enabled       :-)       2014 - 06 - 06 02 : 44 : 41

Nova - compute mycomputenode Nova enabled :-) from: 44 :

If what you see is:

Nova - compute mycomputenode Nova enabled XXX the - . - . the following:

Starting this service will solve these problems

/var/log/nova/compute.log can see the error message in all two files

/var/log/nova/scheduler.log

2. I have also met because the number of virtual machines created in OpenStack has exceeded your set limit and you can try to delete several in the creation.

Error:failed to launch instance "Win7": * Try again later [Error:no valid host was found.].