平素からの当店に対するご愛顧に感謝しております。

。

Thank you for your continued patronage of our store.

Literal

Usual-from our-store [toward-に対する] honorable-patronage [to-に] grateful am.

平素からの is 'from usual times / ongoing.' ご愛顧 is 'patronage/loyal support' — a very formal commercial term. に感謝しております is 'I am grateful' using the humble おる. This is a stock business greeting used in letters, emails, and announcements to thank regular customers.