GA4 not updating until the following day

Setup GA4 a few days ago and noticed that on the home screen the "Sessions" etc. count stays at zero, even though I have had visitors (they show in real time). The following day the sessions seem to show but not on the actual day they happen. With UA they used to appear within a minute or two.
Google Tag Manager is setup and I have put the relevant GTM code on my website. Also using MonsterInsights on my site.
Have I done something wrong? WordPress ...