It's happening in this beta I have never seen this in the other versions, you can't select your classic skin (HD or old one)
Even if you are online and sign in, the skin won't be able to select, if you had a skin pack, you need to press Equip button then select your custom skin.
Thank you for your report!
We're tracking this issue in MCPE-151507, so this ticket is being resolved and linked as a duplicate.
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