Ryobi ss26 trimmer puller cord won't retract

replace the starting pull cord Graeme, Check the attached links,instruction and guides, Good luck
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WeedEater string pull repair STRING WON RECOIL FeatherLite XT260

Fixing The Pull Cord to STIHL Weedwacker

How to Fix the Starter on Ryobi Trimmer

String Trimmer Starter Repair

the ryobi expand-it is just a power head ( motor ) that you can attach any ryobi or like attachment to
There is no reason why attaching a pole trimmer would affect the recoil of the starter rope as it just slides onto the drive at the end of the shaft
the fix will require the removal of the cover and the tool will be in a selection of bits that you can get from a good tool shop or auto parts shop
from memory it is a 6 point star around 3mm in size
the failure to recoil is normally a broken coil spring

Are you using a new plug,sometimes a used plug look's good,but doesn't work.

first pull your spark plug out to make sure you don't have cylimder full of gas and get back with us

well its not going to start with electric because the cord is out of it...
just take it apart becareful do not pull the recoil out or your in a mess....
but this should help you out if you need to know more just ask...

the re coil spring is broke or sliped inside

You didn't list the model but those little rewinds are typically built very similarly.
It may sound a little crazy but it works, take the unit to a power washer such as a car wash and blow out the gook in the rewind with lots of hot soapy water and then rinse. Then using a probe or small screwdriver get the rewind unstuck. If it retracts you’re good to go if not let me know as you may have a broken piece in there and I'll need the model to know what to do next.

http://www.ereplacementparts.com/ryobi-ss30-ry30002-string-trimmer-parts-c-7931_15633_15651.html
This is a parts site for you with a schematic so you can see what is going on. I think your return spring is either broken or out of it's keeper. Check it out. hope this helps.

try oiling into the shaft that turns the head,

What model number is your Ryobi?