The claim is not true. In fact, high-ranking representatives of invited countries attended the commemorative events in different Polish cities to mark the 80th anniversary of WWII.
On September 1, the event devoted to the 80-year anniversary of the outbreak of World War II took place in Wieluń, Poland. It was opened with speeches from the President of Poland Andrzej Duda and the President of Germany Frank-Walter Steinmeier. The event went on in Warsaw and was attended by the Chancellor of Germany Angela Merkel, American Vice-president Mike Pence, British Foreign Minister Dominic Raab, French PM Édouard Philippe, Lithuanian President Nausėda Gitanas, Latvian President Egils Levits, Estonian President Kersti Kaljulaid, Czech President Miloš Zeman, Slovakian President Zuzana Čaputová, Hungarian President János Áder, Ukrainian President Volodymyr Zelensky, Georgian President Salome Zourabichvili, Croatian President Kolinda Grabar-Kitarović, Iceland’s President Gudni Jóhannesson, Deputy Minister of Foreign Affairs of Azerbaijan Mahmud Mammadguliyev, and others.