Please help us help you and fill where relevant:
LimeSurvey version: 6.15.22+
Own server or LimeSurvey Cloud: cPanel / own server.
Survey theme/template: don't know because I can't access the admin panel.
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Hello,
After trying to enter de admin panel, I got this message:CExceptionApplication runtime path "/home/iciorgpt/public_html/estudos/application/runtime" is not valid. Please make sure it is a directory writable by the Web server process.Do you please me solve this issue?
Many thanks!

Hi, this is just to add that I made a restore of the database and the directory (where LS is installed) and the issue persists.

CExceptionApplication runtime path "/home/iciorgpt/public_html/estudos/application/runtime" is not valid. Please make sure it is a directory writable by the Web server process.

Looking at the error message, I don't know why you would restore the database.

The error messages rather points to an issue with rights on directory level, so check if the folder it mentions is writable.

Tysm for your input.
Indeed, I had to create two new folders:

/home/iciorgpt/public_html/estudos/application/runtime
/home/iciorgpt/public_html/estudos/tmp/assets

I really have no idea on how these folders disappeared.
Now it is working again.