Trying to create multisite – network created but then get 404 page

Hi, I wasn’t involved with the original set up of our site, and unfortunately I’m not very experienced in the technical details of it, so would appreciate some help. I followed instructions to create a network / multisite so we can have two language versions of our site. Seems the network was created ok. I now see a new option in the black menu bar (top left) that reads “My Sites” and when I roll-over, it lists two site options: Network Admin with its related menu and our main site with a smaller menu of options. If our original site is selected from this drop down, I go to the usual dashboard and it looks like normal. If I select the Network Admin option, it takes me to a 404 page. Any suggestions?

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