Pipenv: I can install from PyPI private using skip-lock only

I have python package in a private PyPI in Azure. I want to install it in other project, but it only works with pipenv install --skip-lock. This minimal Pipfile should work without problems

[[source]]
url = "https://pypi.org/simple"
verify_ssl = true
name = "pypi"

[[source]]
url = "https://${USERNAME}:${TOKEN}@MyUrl"
verify_ssl = true
name = "example"

[packages]
MyPackage = "*"

[requires]
python_version = "3.8"

But when I do pipenv install, I get this error

pipenv.exceptions.ResolutionFailure]: Warning: Your dependencies could not be resolved. You likely have a mismatch in your sub-dependencies.
  You can use $ pipenv install --skip-lock to bypass this mechanism, then run $ pipenv graph to inspect the situation.
  Hint: try $ pipenv lock --pre if it is a pre-release dependency.
ERROR: No matching distribution found for MyPackage

But when I do pipenv install --skip-lock I can install it without problems.

I tried both in Windows and in Linux with many versions of pipenv, and I get the same error. This is strange because I always used this and from one day to another it stopped working.