try and copy /etc/skel/.zshrc to home.
the .zshrc in home should look like this:
# Use powerline
USE_POWERLINE="true"
# Source manjaro-zsh-configuration
if [[ -e /usr/share/zsh/manjaro-zsh-config ]]; then
source /usr/share/zsh/manjaro-zsh-config
fi
# Use manjaro zsh prompt
if [[ -e /usr/share/zsh/manjaro-zsh-prompt ]]; then
source /usr/share/zsh/manjaro-zsh-prompt
fi
I think you installed Manjaro when the p10k prompt was not used by default, so when the p10k was included through an update, it did not overwrite your user zsh config (~/.zshrc).