What things?
In order for Grub to detect and add a Windows entry, both systems need to be installed the same way (both MBR, or both UEFI).
If this is the case, make sure GRUB_DISABLE_OS_PROBER=false is set in /etc/default/grub and update Grub. Do not reinstall grub package like you did, but execute:
sudo update-grub
