Edward's claim on France was bogus
In 1316, King Louis X died, leaving behind a daughter, Joan. It was an unprecedented situation, because since the Capetians took the throne in 987, the reigning king always had a son. But in this case, they didn't know what to do, because they had no law of succession; the king's oldest son inheriting was customary. So, nobody knew whether Joan should succeed or her uncle, Philip. So, the Parliament of Paris voted to exclude women. Giving the throne to Philip.
Ironically, Philip (V) himself sired 4 daughters but zero sons. So, when he died in 1322, the throne passed to his brother, Charles.
In 1328, the male line of Louis, Philip, and Charles went extinct, triggering another crisis. Isabella, the sister of the brothers, claimed the throne of France for her son, Edward of England, as the only grandson of the Iron King. However, the Parliament of Paris voted and decided that because women were already excluded, they could not pass the throne to their son. Thus, the throne was given to Isabella's cousin, Philip of Valois.
Following this. Edward accepted Philip's accession. However, in 1340 Philip invaded Edward's land in Aquitaine, and in response Edward claimed the throne of France based on his earlier's claim.
His claim was that the succession change of 1328 didn't apply because Charles died before it was passed, thus as the only grandson of the Iron King, he should have inherited in 1328. The issue with this is that, in 1340, Edward's claim no longer made any sense. Edward was no longer the only grandson of the Iron King, but Joan had mothered Charles of Navarre, whose claim was superior to Edward's.