This is because when the game is offline, it won't connect to the Minecraft services which means your skin won't load. A way you could fix it is by making a resourcepack to replace the alex skin with your skin.

thank you i appreciate the help

quick question how do I do that?

This report is a duplicate of MC-101579, which was later resolved as invalid. The reason for this is because this issue is most likely caused by malware or other software that is interfering with Minecraft. Please see the Moderator Note attached to the parent ticket to potentially fix this issue.

Download this and unzip it, then go into assets\minecraft\textures\entity and replace steve.png and alex.png with your preferred skin(s).

Thank you for your report!
We're tracking this issue in MC-101579, so this ticket is being resolved and linked as a duplicate.

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