It’s only been one working day so I definitely wouldn’t worry! They won’t have got round to processing the application yet, it won’t be anything meaningful.
DD only heard from Man Met and Northumbria within 24 hours - she’s already achieved 3A*s at A level and they only ask for BBC/BCC. The others both took a few days (with asking grades of AAB so again she’d still exceeded that significantly) and Durham took over a week I believe. It totally depends on the university, course, time of application - 1 working day is definitely not cause for concern!!
to get you through this stressful time...