There is a theorem (e.g. proposition 9.6 in Atiyah-MacDonald) that states that a fractional ideal $I$ of a domain $R$ is invertible if and only if it is finitely generated and it is locally invertible everywhere, that is $I_\mathfrak{p}$ is invertible for every prime $\mathfrak{p} \triangleleft R$.
What would be an example of an ideal which is locally invertible at every prime ideal but that is nonetheless not invertible? This ideal would necessarily have to be non-finitely generated.
I've only been able to find examples of non-invertible ideals that are non-invertible because they're non-invertible at some prime ideal.