If above solutions are still not working then you can follow below steps

1. clear npm cache:

npm cache clean --force

2. Reset Npm Registry

npm config set registry https://registry.npmjs.org/

3)Then use below command

**npm install next@canary --registry https://registry.yarnpkg.com

[** Optional ]

# Try to clear dns cache (Windows)

ipconfig /flushdns

# Then try this again

npm install next@canary