A few considerations:

-If a printhead has been starved of ink for a long time, it may have burned itself out by printing with air instead of ink. If this is the case, that printhead will not recover with the installation of new seals.

-Even if a printhead has been starved for only a short period, if the internal ink diaphragm has deflated too much, it will sometimes not allow ink to re-inflate it, and the printhead will remain permanently starved.

-Sometimes the electrical connection between the printhead and the carriage is poor. Make sure to clean off the printhead contacts as well as the contacts on the carriage. If either of those surfaces feels tacky, you've still got cleaning to do.

-If the drop detector sensor is obscured by ink overspray, it will not properly detect the ink droplets, and the printer will not complete print system setup even if the printheads are working with perfect quality. The sensor may require cleaning.