The requirement is verified support
A stud finder is a tool for locating clues about framing. It is not the support itself, and owning one does not guarantee a suitable mounting point. If you do not have one, the key question remains whether you can reliably establish the wall construction and the attachment required by the bracket.
Do not rely on tapping alone
A hollow or solid sound can be misleading because finishes, insulation and wall assemblies vary. Magnets may locate fasteners, but a fastener location does not by itself establish the center, size, condition or material of the structure behind the wall.
Understand the limits of assumptions
Do not assume every wall has evenly spaced wood studs or that the first detected edge identifies a safe drilling point. Old repairs, additions, metal framing and decorative surfaces can change what is behind the finish. Electrical cables and plumbing also need consideration before drilling.
Choose an appropriate next step
Borrowing or obtaining a detector suited to the wall may help, but uncertain results need verification. Building information can assist where available. If the proposed mount instructions and the observed construction do not match, pause and have the wall assessed.
Do not replace a missing stud finder with an improvised collection of drywall anchors. Some products permit particular hollow-wall installations, but that approval is specific to the complete system and conditions. It does not apply to every television or extending mount.
When contacting TV Installation Pros, describe the finish and share a wall photo. Let us know if another bracket was previously installed or if you have already made exploratory holes.