If you previously had a pin active for the parental controls in the Play Store settings and have removed it by deleting the data under the Phone's app settings (not the Play Store app), then you need to set a pin again in the Play Store settings. After that, you can either leave the pin active with full access, or set the level you want to filter again, or deactivate the pin.
A forgotten pin can be reset / deleted by going to your phone settings...
apps
Google Play Store
Storage
delete data
But like I said... you then have to set a pin again in the Play Store settings under parental controls to complete the reset. After that, you can do whatever you want with the parental controls