I'm experiencing a SOLR error that makes impossible authentication on Alfresco. Server worked correctly, but after a reboot:

From logs I saw a recurrent error on SOLR (it appears each 10 secs):
solr6_1 1 2022-02-17 07:17:50.113 ERROR (org.alfresco.solr.AlfrescoCoreAdminHandler@37 Obd86d_Worker-14) [ ] o.a.s.t.AbstractTracker [alfresco / MODEL@655729129 / IT #1645082270021] Tra cking failure. See the stacktrace below for further details.
solr6_1 1 org.alfresco.error.AlfrescoRuntimeException: 01170040 api/solr/modelsdiff return status:404
solr6_1 at org.alfresco.solr.client.SOLRAPIClient.callRepository(SOLRAPIClient.java:1596)
solr6_1 at org.alfresco.solr.client.SOLRAPIClient.getModelsDiff(SOLRAPIClient.java:1103)
solr6_1 at org.alfresco.solr.tracker.ModelTracker.trackModelsImpl(ModelTracker.java:313)
solr6_1 at org.alfresco.solr.tracker.ModelTracker.trackModels(ModelTracker.java:275)
solr6_1 at org.alfresco.solr.tracker.ModelTracker.doTrack(ModelTracker.java: 235)
solr6_1 at org.alfresco.solr.tracker.AbstractTracker.track(AbstractTracker.java:242)
solr6_1 at org.alfresco.solr.tracker.TrackerJob.execute(TrackerJob.java:60)
solr6_1 at org.quartz.core.JobRunShell.run(JobRunShell.java:202)
solr6_1 at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:573)
Any ideas?
Thanks!