Same issue here.
Similar thread (I just replied there):
https://support.lastpass.com/s/question/0D5TP00000L5zjv0AB/has-anyone-had-any-issues-accepting-items-that-are-shared-with-them-i-have-a-few-that-i-am-trying-to-accept-but-when-i-click-on-accept-the-screen-goes-slightly-grey-and-nothing-happens-cant-figure-out-why-it-wont-let-me-accept-thanks