this isn’t related to GeneratePress.
A subdomain would require a separate WordPress install ( or be part of a multi-site ).
If you’re having difficulty setting up the subdomain you should speak with your hosting company.
Thanks, I shall check with my hosting company.
But as an expert, could you also give me your opinion – should I use a sub-domain or just my main domain for the store? I am confused about this.
Will having the store on the main website increase the page loading time?
Not sure why people use sub-domains for store, but I am not very keen because that would mean that I will have to maintain two separate websites, which is more work.
Please provide your opinion so that I can make a decision.