You’ll have to set it in the store config options, as you are calling the Pow.Store.CredentialsCache directly. :credentials_cache_store is only used in Pow.Plug.Session plug.

So do this instead:

store_config
|> Keyword.put(:ttl, :timer.minutes(28800))
|> CredentialsCache.put(access_token, {user, [renewal_token: renewal_token]})

Or if you want to use the same setting as in your config:

{_store, opts} = Config.get(config, :credentials_cache_store, nil) || raise "No `:credentials_cache_store` config option set"

store_config
|> Keyword.merge(opts)
|> CredentialsCache.put(access_token, {user, [renewal_token: renewal_token]})

I strongly encourage you to keep the TTL much shorter than what you got. OWASP recommends the following:

Common idle timeouts ranges are 2-5 minutes for high-value applications and 15-30 minutes for low risk applications.