Hi Jim....welcome to the Forum
This is an issue I am experiencing on a constant basis nowadays.
Having successfully fitted numerous belts over the years and never had any issues, but recently I have had a spate of 'squeeky' belts.
I am quite sure it relates to the country of manufacture (China) and even though the latest 'squeeky' belt I fitted was a Gates belt it was still made in China, which to me signifies that it is of poor quality (e.g. possibly not much rubber content?).
I would source a reputable make of belt and preferably not one made it China .... this should resolve the issue.