Not sure what is going on there.
However, for things like this I use this CSV to Tabs on Clipboard Automator Services (Dropbox download).
To install just double-click the downloaded .workflow package and give permission at System Preferences > Security & Privacy. Also make sure 'Automator.app' is checked at System Preferences > Security & Privacy > Privacy > Accessibility.
Thereafter to use all you have to do is find the downloaded csv file in Finder, right-click or option-click it, and in Finder's File > Services menu choose 'CSV to Tabs on Clipboard'. You would then choose the ; at the prompt.
Then click once in a Numbers cell where you want the data, and type command-v or choose Edit > Paste and Match Style from the menu.
I find this easier than File > Open a csv file in Numbers, then having to move the data where I want it. Also this Service can handle many delimiters that you are likely to encounter, including ; .