Election officials are following the orders of both PA State and SCOTUS.
The last time I checked, PA election officials declined to allow poll watchers watch the ballot counting, even after a PA appellate court ordered them to.
Trump is arguing that they they are already fraudulent and should not be counted and a whole bunch of other nonsense.
The state law is clear, in PA, the deadline to receive ballots is 8 PM on election day. Any vote received after this deadline is not a legal vote, and as such should not count. The term "fraudulent" may or may not be appropriate, however, these are not votes that should be counted.