We have two Moto G5+ phones. Now and then, they do weird things - like voicemails arrive without a call. Then we have to reactivate the phones. My wife finds this annoying, because she doesn’t feel competent to correct such things. We’d really like to know how this occurs.
Welcome to the community. Your issue sounds data/Internet related. Typically the reactivation prompt happens when the phone is unable to contact us over data/Internet for a few days. At some point the token (a security thing) goes stale. Do you possibly turn off data manually on the phone or have a data saving app? This would explain the other abnormalities since voicemail needs to come in over data and will come in later when the phone gets data… You do not need a data plan but we need access to data.
We also have a help article about a known issue with the Moto G5+ asking to be activated. Please see if the fix described in the article below helps.
The link does the job. Thanks.