Reproduction steps:
1. Open the attached “Bug report.zip” project
2. In the Project files right click on the Merriweather font and create a new font asset (Create > TextMeshPro > Font Asset)
3. Click on the created asset and in the Inspector window click Update Atlas Texture
4. Set the character set to ASCI, generate and save the Atlas
5. Select the texture inside the created asset
6. Click on the three dots in the Inspector and choose “Debug” mode
7. Observe the ‘Is Readable’ property value

Expected result: The ‘Is Readable’ property is set to true
Actual result: The ‘Is Readable’ property is set to false

Reproducible with: 2021.3.34f1, 2022.3.17f1, 2023.2.4f1, 2023.3.0b1

Reproducible on: Windows 11, macOS 13.6.3
Not reproducible on: no other environment tested

Notes:
- Restarting the project fixes the issue and the value is checked automatically
- Reproducible on a new project