Does an offline website affect the SEO score/progress?

Hello, I have a website that we have been doing SEO work for 6 months, backlinking and on-site SEO. No website clients/visitors yet, however currently the website is down due to a technical error, that’s going to cost a bit to fix. And my question is the longer the website is offline the worse the SEO gets? Or once recovered the whole progress will be recovered quickly? In other words should I recover the website ASAP or can it be in 3-4 months?