First, make sure you give it up to 5 minutes. If it's been at least 5 minutes and the permissions haven't changed, then it's a problem with the TortoiseSVN cache. You can follow the instructions at:

https://tortoisesvn.net/docs/release/TortoiseSVN_en/tsvn-dug.html#tsvn-dug-general-auth

to clear the cache and ensure it's using the correct credentials.