unable to accept admin invite

Hi this facebook page have no quality issues, but now we are unable to accept admin invites, what is a good solution for this problem?

EDIT- yes we tried on mobile, mobile lite, says error please try again later

Facebook's Help page on accepting Page access describes two routes: the Review Invite button in the invitation email, or the notification on Facebook (tap it, then Review Invite, Next, Accept). Since you've tried the mobile app and Lite, the email route and a desktop browser are two distinct surfaces still untested, and the invite may be waiting in one of them even when the app throws an error.

If it fails from every route, the admin side has a documented option: the Help page on giving and removing Page access says someone with full control can edit or remove someone's access at any time, managing it after switching into the Page. So the admin can remove the pending invitation and send a fresh one. Whether a stale invite is your actual cause I can't say from here - treat re-sending as a quick experiment, not a guaranteed fix.

And if re-sending doesn't work either: "please try again later" is generic error text that doesn't identify the cause, so the useful next step is documenting exactly where it fails (which surface, which account, which step) and sending that through Facebook's Report a Problem flow.

I’ve encountered this issue before. it’s a technical glitch on Fb end. Ask the person who invited you to be an administrator to cancel that request, then have them send the invitation again it should work within about five minutes.

Your personal profile has not been associated with the Business Manager (BM) for long enough to accept the invitation.
Please contact the person who manages the BM to confirm.

If the previous invitation has expired or a system error has occurred, ask the owner or a senior administrator to cancel the old invitation and send a new administrator invitation to your account.