Hello Shelagh Tillott-Booth,
If you are not seeing any extensions installed in Chrome I would first try to clear the browser’s cache, if that does not work I wonder if you are using a VPN with Ad-Block enabled.
In Chrome
On your computer, open Chrome.
At the top right, click More.
Click More tools. Clear browsing data.
At the top, choose a time range. To delete everything, select All time.
Next to “Cookies and other site data” and “Cached images and files,” check the boxes.
Click Clear data.