This is a 2013 application which means that it doesn't have support for the latest Android release or Samsung S7 Edge. However, you should know that changing IMEI is against the law, but there are service shops that can do it although you won't have much support for the phone afterwards. The IMEI is unique to each of the phones released and it should stay that way.
Contact a local service shop or Samsung directly and explain that the IMEI has been lost, probably after ROM installation that modified the EFS partition.
