soft wood cuttings in propagation system won't root for me :(

I was absolutely certain things would root as easy is you say!
I live in central Ohio. The last Spring frost date was about May 20.
May 23, I took several soft wood cuttings of a variety of shrubs and trees, and placed them in the propagation system's "fish tank" covered box - just as instructed on your website.
And, I followed all the instructions as per starting them in the shade - then moving to sun - keeping the soil moist, etc.
Two weeks later - no roots - on any of them.
Figuring I had attempted it too early in the season, I tried the very same process again starting on June 12.
Today, June 20, I checked for root development. Absolutely nothing on any of them.
I'm stunned!! What am I doing wrong?!!
Thanks for any and all help and advice!

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