When your Buyer pays your invoice it undergoes some automated security checks. During this time your invoice status will show as "Pending". In the majority of cases this processing takes just minutes or at peaks times a few hours, however in case extra security checks are needed it may take up to 3 working days.
If your invoice is Pending and it has been less than 3 working days (i.e. excluding Saturdays, Sundays and UK public holidays) since your Buyer paid your invoice then simply check back again later and you should find that the funds have been released to your PPH wallet.
Only get in touch with PPH Customer Support if it has been more than 3 working days since your Buyer paid your invoice.