Rule #4 :
The twelve Rules of Mikrotik Club
Quickset is definitely not up to the task.
You should make sure that (now) you can access it with Winbox via MAC (this way you can fiddle with IP's as much as you want.
Then it is recommended (by me) to ADD an IP address to the interface, then test it works (connection via Webfig and with Winbox via IP), and only once this is confirmed remove the old address.
You may need to change some settings on your PC or on the n-Rays, but having Winbox functional, both via IP and via MAC is essential to have a "safe entry point" in case of mis-configuration.
In any case BEFORE making any change you should do an export of your configuration and save it (better be safe than sorry).
Instructions to save an export to file (and if needed post it on the forum, screenshots are rarely the "right" way to exchange information) are here:
Forum rules - #5 by gigabyte091
None of my business, and not related to your current issue, but a /16 network (65,534 possible devices) is rare in anything but large corporate networks (and even there the networks are usually fractioned in several smaller subnets).