If there is one covenant, why are there different conversion requirements?

Because the movements differ on what the covenant requires and who is authorized to administer it. The same covenant is interpreted through different halachic frameworks, so a conversion accepted in one may not be accepted in another.

This is one of the most disorienting facts for a convert-to-be. Understanding it as a consequence of disagreement over authority — not of the covenant itself — helps.

Machloket /makh-lo-KET/

A disagreement; many are preserved as legitimate.

• Orthodox: requirements are fixed by halacha and administered by recognized Orthodox batei din; not all conversions are accepted.
• Conservative/Masorti: halachic requirements interpreted through the movement's law committee.
• Reform: requirements set by the rabbi and community within Reform principles.

As the movements diverged in the 19th–20th centuries, each developed its own beit din standards, so a single underlying process fragmented into several recognized-within-but-not-universally variants.

The covenant is one; the requirements differ because the interpreters differ.

Whether the divergence is legitimate pluralism or a failure, and which conversions other communities must recognize.

Choose the community you want to belong to and convert through its process; understand in advance which other communities will recognize it.