I bought Java just know, and I'm pretty sure I have bought it before, and Minecraft Launcher says that I do not own it and says I need to buy it to play. Even though I just bought it. I tried to sign out and sign back in and close and open it and still says I do not own it.
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We're tracking this issue in MCL-16570, so this ticket is being resolved and linked as a duplicate.
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Please check out this help article: https://help.minecraft.net/hc/en-us/articles/360029643892-Can-only-play-Minecraft-demo-Java-Edition-
If that doesn't solve your issue, please contact Mojang Support.
Quick Links:
📓 Bug Tracker Guidelines – 💬 Community Support – 📧 Mojang Support
📓 Project Summary – ✍️ Feedback and Suggestions – 📖 Game Wiki