site keeps crashing after upload of theme

Further to my email on 2 May and correspondence with Ismail, one.com’s help team and I have tried repeatedly to get the theme to work. Every time it is chosen on the wordpress dashboard, it crashes. I tried both through filezilla and the dashboard. I can provide copies of the screens as well as chat transcript with one.com but need somewhere to do it. I am ready to pull my hair out and have tried everything I could think of. What could be the problem now? I’ve had to change the theme to twenty twenty-four just to regain access to the dashboard.