How to fetch all remote branches?

Check you git config --get remote.origin.fetch refspec.

It would only fetch all branches if the refspec is

+refs/heads/*:refs/remotes/origin/*

If the refspec is:

+refs/heads/develop:refs/remotes/origin/develop

Then a fetch would only bring back the develop branch.
This is typical of a git clone --branch develop --single-branch.

you can check your branch cat .git/config in terminal

[core]
    repositoryformatversion = 0
    filemode = true
    bare = false
    logallrefupdates = true
    ignorecase = true
[remote "origin"]
    url = { git remote url }
    fetch = +refs/heads/develop:refs/remotes/origin
[branch "develop"]
    remote = origin
    merge = refs/heads/develop

and git remote update but not update remote branch. you will replace origin fetch

first, check remote fetch git config --get remote.origin.fetch

+refs/heads/develop:refs/remotes/origin/develop

second, unset remote fetch use git config --unset-all remote.origin.fetch and add another git config --add remote.origin.fetch +refs/heads/\*:refs/remotes/origin/feature/\*

then, you can check replace remote git config --get remote.origin.fetch

+refs/heads/*:refs/remotes/origin/*