Patricia,
We cover a lot of these things in the book, I'll plug that at the end. A couple of things I see that may be causing you not to have banner fruiting.
Shiitake- loves oak, we also had great success with Beech (alder and hard maple do real good also) Oyster is not a fan of oak but Aspen and poplar
trees (also mulberry) So depending on what you used tree species wise that may have a real impact on your mycelial run.
I never "planted" shiitake logs (reishi, lions mane and nemeko we did) I even went so far as to put pine shredding down and putting my logs on
pallets, this way existing
mushrooms could not colonize the log. Shiitake are not as aggressive as oyster, and there are mushrooms out "in the woods" that more aggressive.
You also need to have a proven spacing for your holes, each species is a little different. Also I hope you sealed your inoculation sites, if you did not wax them they will dry out, and insects will eat the spawn also.
"Frozen" will not affect shiitake they can freeze solid, their caps will crack but the will resume growing. Oysters can take a freeze, but not for a long period of time.
Also the strain you used will vary in it's time from inoculation to fruiting. We used to have a cold weather strain that took 1 1/2- 2 years before we saw mushroom, they were awesome but they took a long time. I also do not know where you live ie. your climate which will also affect your mushroom growing.
Hope some of this helps and lastly for a beginner www.mycelialmayhem.com and you can order a copy that covers everything above plus so much more.
Dave