Adenoviruses are non enveloped. You can insert the gene coding for IAV-HA into an adenoviral vector for expression in a target cell, but it won't be expressed on the surface of the viral particle.
Presume you mean you didn't see HA at the cell surface? Some avian HAs with multibasic cleavage sites (HA0 is cleaved by furin and other Golgi proteases) require co-expression of the M2 channel in order to reach the cell surface. This is common in H5 strains, less so in H7, but strain-specific.
When you are inserting HA genes from avian influenza virus to adeno virus it's expresse
d in genes but HA is not formed on the surface . Moreover adeno virus is non enveloped so HA property is not expressed on the surface and hence you will not findhaemagglutinin on assay.