Some people may encounter event tracking on GTM, which can be found in GA3 (Universal Analytics), but not in GA4.
GA4 has a relatively serious data delay, It can take up to 24 hours for newly created events to be shown in the reporting, many of your reports and explorations can take 24-48 hours to process data from your website or app. Read more：GA4 Data Delay： Data Freshness
Suggestion: Check back in a few days.
If Google Signal is turned on, there are few data and no data thresholds are exceeded, in order to protect user privacy, GA4 will not display some data. Read more：Understanding Data Thresholds in Google Analytics 4
Suggestion：Select 「Device-based」 for 「Reporting Identity」.
GTM is Not Released
If you configure this event in GTM, the Preview is normal, but it is not released, which may also result in no data.