Hi everyone,
For HP Printers you just need to shake the cartridge and then place it back into the tray in the printer.
Better to shake it with the original cap inserted as there is always a risk the ink might flow out, anyway such risk is limited.
After shaking the cartridge I recommend to try a print test from the printer maintenance menu, as well as some other procedures like cleaning cartridges and ink nozzles (still from the maintenance menu) as that should provide that additional push to unblock the cartridge.
Hope this might help you all, cheers