Apply to freshly washed, clean, dry underarms
Give your body time to adjust to a new deodorant, usually 1-4 weeks. stick with it for several weeks for your body to adjust.
Try an armpit detox if coming from a conventional antiperspirant (which means you will be sweating more now and your body needs to adjust)
https://www.healthline.com/health/armpit-detox#purpose
If sensitivity is not a big concern, try a line of baking soda deodorants to see if it works better with your body’s chemistry.