You may need a Base Plate.

The Following require a round base

• RAM‑HOL‑AP20U — iPad Mini 4 & 5
• RAM‑HOL‑AP36U — iPad Mini (A17 Pro) & Mini 6
• RAM‑HOL‑AP23U — iPad Pro 11 / Air 4–5 / Air 11 (M2)
• RAM‑HOL‑AP31U — iPad 7th/8th/9th Gen
• RAM‑HOL‑AP17U — iPad 6th Gen / Air 1–2 / Pro 9.7
• RAM‑HOL‑AP22U — iPad Air 3 / Pro 10.5
• RAM‑HOL‑AP24U — iPad Pro 12.9 (3rd Gen)
• RAM‑HOL‑AP21U — iPad Pro 12.9 (1st & 2nd Gen)

The Following require a diamond base

• RAM‑HOL‑AP38U — iPhone 13/13 Pro/14/14 Pro/15/16
• RAM‑HOL‑AP39U — iPhone 14 Plus/Pro Max/15 Plus/16 Plus