Skins do not always work in the offline version of Minecraft, but now this problem can be easily solved using the OfflineSkins mod.
Mod OfflineSkins for Minecraft 1.14.4/1.14.3/1.13.2
Add the desired skin to the mod folder and try playing a single game. Now you will have a beautiful skin, regardless of whether you have a pirated account or a license.
1.14.4 – OfflineSkins-Mod-1.14.4
1.14.3 – OfflineSkins-Mod-1.14.3
1.13.2 – OfflineSkins-Mod-1.13.2