Hi, I assume that you mean that your Clock Face has changed form the standard Vers 2 Waveform to Sundial, also by Fitbit. Try to restart your Versa several times by pressing and holding the left button untill you see the Fitbi logo and see if you can change it back now to Waveform by going to clocks - all clocks - choose by Fitbit: dispaly them all and scroll to Waveform, press it and press "Select". If that does not work, I'm afraid you wil have to perform a Factory Reset: Settings - Device Info - press that and scroll to Factory Reset and press that. Mind you that you need to do the setup of your Versa 2 all over again as it acts like a brand new device just coming out of the box.
BTW: What you can try to do if suggestion 1 does not work and before doing a FR, is to install another Fitbit CF, f.i. Light. If that succeeds, restart your Versa, go back to CF and see if you can Waveform CF now. If that works, you do not have to perform a FR. If you have to do a FR, sync your Versa before that with the Fitbit app otherwise you will loose valuable data.
Good luck and regards, kuzibri
