When EM is trying to do a failover from a protected server to a spare sever and gets stuck in a state of Data Restore Pending, it is most likely due to Password Strengthening being Enabled on the Exacq Server.
If it is Enabled on either the Spare or Protected Server, you will not be able to failover and back successfully until you resolve this.
Please refer to KB:6090
https://support.exacq.com/#/knowledge-base/article/6090