Can you identify the iBook G4? There were several different builds across the years
the G4 was manufactured; the first models all use PC2100 DDR266 200-PIN SO-DIMM.
Only the last iBook G4 12-in + 14-in from Mid 2005 use the PC2700 DDR333 200-pin
SO-DIMM; and this chip is the same one that matches the iMac G4 USB2.0 user upgrade
slot specification.
There were two models iMac G4 with 1.0GHz processor; one uses PC2100 DDR266 200-
pin SO-DIMM while the later model uses PC2700 DDR333 200-pin SO-DIMM chips...
Some models can use the later spec RAM chip (at slower original memory speed due to
limits on the computer hardware) so the DDR333 is seen as DDR266 in older Mac G4s.
A DDR266 SO-DIMM from an older iMac G4 probably won't work in later model iBook G4.
I have a Mid-2005 iBook 12-inch 1.33GHz model that can use the same upgrade RAM chip
the last models USB2.0 iMac G4 (PC-2700 DDR333 200-pin SO-DIMM) in a direct swap.
And I have a few of these iMac G4 1.25GHz models. The factory RAM chip is a different spec
and pin count, and requires special take apart ritual to upgrade to higher capacity.
You could swap the chips back to where they came from to test and see if they both are OK.
If you touched the metal contacts on the RAM, that may have shorted the chips; or the RAM
was not seated fully (if the parts were correct in the first place.)
And you may have to reset the PMU in the iMac G4 to see if the change in RAM is recognized
Resetting the iMac (Flat Panel) Power Management Unit (PMU) - Apple Support
As a last resort; this reset could deplete the PRAM battery if not done correctly. And in order
to replace the clock battery, a major takeapart is required. Enough effort to also consider an
upgrade of the factory slot RAM. Thermal paste, extra tools, & careful handling are required.
Mr Totes iMac G4 (USB2.0) Take apart:
http://www.mrtotes.co.uk/page1/page1.html
iMac G4 Take-apart for Drive, RAM, battery:
http://www.xlr8yourmac.com/systems/imac_g4/imacg4_takeapart.html
This has been a difficult reply to formulate and I've written this perhaps four times, with details.
The everymac.com site & a download of mactracker.ca (for offline database) are recommended.
Since the time here is now approaching 1:40AM (AKDT) I'm going offline now.
Good luck & happy computing! 🙂