Never hurts if there is in fact a Firmware Update that is available for your G5 that has not already been applied.
General speaking Larry O'Conner over at OWC is a really fair guy and some OWC memory was sold with a lifetime warranty.
Tho that likely only applies if you have the recipe or some form of proof of purchase.
Anyway, never hurts to email them if you have the part# of the RAM to ask what Mac's it's compatible with. Last time I emailed Larry direct he sent me a direct reply and fixed my issue or had it fixed.
May happen you just need to email support@owc or whatever as Larry is the CEO and I'm not sure he has the time these days to reply to each email like he did for me back in the early 2000's.
Maybe they still have someone it tech support that can help you with this issue if it's just not something that has been forgotten or nobody there even ever worked in support in the PPC days.
Tho, generally speaking OWC knowledge of Mac's, and their online knowledge-base likely can tell you if it will work or why it won't.
Assuming you have the part# of the RAM.
