When are scientific claims accepted? And when are they questioned and/or rejected?

The answer is; When the scientific claims are accepted when they are corroborated by scientific data. Experiments are set to collect data and make observations regarding the claims. Based on the outcome, the claims (which will be formulated as a hypothesis) will be accepted or rejected. When the experiment is replicated by different independent scientists and producing predictable results, then the claims become a scientific fact.