Dear Eugene,
About Synology, Note that all Synology comes with a reset button, that reset Synology Configurations to factory setting. The reason why your NAS shows configuration lost is due to re-format of configurations.
FYI, You need to re-install the NAS with the Same firmware or latest firmware. For this re-installation note following.
1. Re-installing firmware does not format the drives
2. By resetting, You already lost configurations ( Network Settings, Users profiles, Any application installed and it's setting )
3. After re-installing, creating your users afresh, network settings and applications.
NB
Backup your Synology configuration always.
More information
https://www.synology.com/en-us/knowledgebase/tutorials/493