The PowerShell ISE is no longer actively developed and there are reasons not to use it (bottom section). The editor that offers the best PowerShell development experience, across platforms, is Visual Studio Code, combined with its PowerShell extension, which is under active development.
Try restarting the ISE. There should be no difference in what programs you can call by mere filenames, such as "aws" if there is, check your "$PROFILE" file from a regular PowerShell session to see if "$env:PATH" additions are made there that the ISE which has its own "$PROFILE" doesn't see.
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