Not a DOI

The resolution service at https://doi.org resolves DOIs. You have attempted to resolve core/journals/the-british-journal-of-psychiatry/article/crossnational-prevalence-and-correlates-of-adult-attentiondeficit-hyperactivity-disorder/43819B490B72F072154DBDEAFE9807E8, which is not a DOI.

core/journals/the-british-journal-of-psychiatry/article/crossnational-prevalence-and-correlates-of-adult-attentiondeficit-hyperactivity-disorder/43819B490B72F072154DBDEAFE9807E8 may be a Handle (DOIs are a special sort of Handle). If core/journals/the-british-journal-of-psychiatry/article/crossnational-prevalence-and-correlates-of-adult-attentiondeficit-hyperactivity-disorder/43819B490B72F072154DBDEAFE9807E8 is a valid Handle you should be able to resolve it at https://hdl.handle.net.