almost certainly permissions, because the call to disk is not going to use the account you are expecting it to.
when you access any resource OUTSIDE of SQL server, like network shares, local hard drives and folders,
SQL Server uses either the account set up as the proxy account, or if that is left blank(the default) it uses account it starts with to try and access the resource:
or if the above was blank, the account in services:
That account is often an account which has never logged into the domain, and was never assigned permissions to get to the local disk or network share.
so you typically want to create a new user on the local machine or in active directory which would have access to the shared network resources in question, and then to change the startup account that SQl server is using;
here's an example where i put in my account instead, with my domain account and password, and then i can test the shared path i was trying to access/use before;
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