I think this may be a possible solution for the issue, but am not sure.
“The quick answer is that $($_.ipaddress) evaluates to an array of
objects — e.g. [system.object[]] as stated — and arrays don’t have
this method. When you pass an array like this along a pipeline,
powershell “unrolls” it, that is to say it feeds the elements one at a
time along the pipeline; that’s why you see the string instance’s
methods in the get-member output.”