Every artist has that group of gigs that they have tried and tried to book but to no avail. Here are some of the reasons why you may be losing those gigs to others.

Your price was too high. Be sure you do your homework and know what the venue normally pays
Your price was too low. This can brand you as an amateur. Know what you are worth!
You’re not the right fit for the venue. Be sure you’re a good match for the venue before you make the call.
You don’t have a good live video. Entertainment buyers need to know what you look and sound like before they will hire you.
Your website or other marketing materials don’t look professional. No matter how good your act is, you will still be judged by your marketing.
You don’t have experience successfully playing that kind of venue. Venues need to know that you can deliver at least as well as the other acts they hire.
The venue requires that you draw fans to the show but you don’t have a large enough fan base. Be sure you have a large mailing list and following before you approach this kind of venue.
You have a reputation of being hard to work with. Word spreads fast among venue owners and managers. They always do their homework before they hire you.
You’re not a good salesperson. Booking gigs requires strong sales skills.
You not as strong as the other acts vying for the same gigs. Know your competition.