While enabling security on a valueset getting error "Pk1ColumnName exceeds max allowed length"

Summary:

We have an existing value-set for one of the segments in Suppliers DFF, that we need to enable security enabled, as it is required to make the LOV visible in the Next Generation Supplier Registration.
When we try to enable security on this existing value-set, we get an error "field Pk1ColumnName exceeds the maximum length allowed" and it is not allowing us to save.

Without enabling security on this value-set, we are unable to make the DFF-field appear with LOV, on the Next Gen Supplier Registration page.

Error Codes
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field Pk1ColumnName exceeds the maximum length allowed