Error : com.neo4j.server.enterprise.CommercialEntryPoint after update to Neo4j 4.0.1

I tried to upgrade to Neo4j 4.0.1
I used 'Upgrade' in Neo4j Desktop, and it seemed to work fine, but when starting my database I get :

2020-03-24 20:04:42.749+0000 WARN The client is unauthorized due to authentication failure.
Erreur : impossible de trouver ou charger la classe principale com.neo4j.server.enterprise.CommercialEntryPoint

I didn't make any backup of my database, which contains ~1.5 millions nodes and about a hundred hours of work. (Yes it's stupid)

Do you know where the error comes from ?

neo4j version
before : 3.5.6
after : 4.0.1

Desktop version

plugins : APOC
(I tried to update it to but cannot start database)

I can clone database but cannot start it.

Note : I tried to downgrade back to 3.5.6 but button 'Downgrade' is inactive, I saw this but it's quite old. Any way to downgrade ?

last logs (I think useless because nothing from the moment I start the update in neo4j.log nor in debug.log, both in 4.0.1 and 3.5.6 folders)

2020-03-24 20:08:59.961+0000 INFO [o.n.k.i.a.i.IndexingService] Constraint IndexRule[id=22, descriptor=Index( UNIQUE, :label2 ), provider={key=native-btree, version=1.0}, owner=null] is ONLINE.
2020-03-24 20:14:38.060+0000 WARN [o.n.k.i.c.VmPauseMonitorComponent] Detected VM stop-the-world pause: {pauseTime=112, gcTime=0, gcCount=0}
2020-03-24 20:23:19.977+0000 INFO [o.n.k.i.t.l.c.CheckPointerImpl] Checkpoint triggered by "Scheduled checkpoint for time threshold" @ txId: 436032 checkpoint started...
2020-03-24 20:23:20.143+0000 INFO [o.n.k.i.s.c.CountsTracker] Rotated counts store at transaction 436032 to [C:\Users\xxxxx.Neo4jDesktop\neo4jDatabases\database-0f434f05-b24a-4d4a-971d-8afaa0bcde3d\installation-3.5.6\data\databases\graph.db\neostore.counts.db.b], from [C:\Users\xxxxx.Neo4jDesktop\neo4jDatabases\database-0f434f05-b24a-4d4a-971d-8afaa0bcde3d\installation-3.5.6\data\databases\graph.db\neostore.counts.db.a].
2020-03-24 20:23:20.476+0000 INFO [o.n.k.i.t.l.c.CheckPointerImpl] Checkpoint triggered by "Scheduled checkpoint for time threshold" @ txId: 436032 checkpoint completed in 499ms
2020-03-24 20:23:20.530+0000 INFO [o.n.k.i.t.l.p.LogPruningImpl] No log version pruned, last checkpoint was made in version 2

Impossible to solve the problem.
I'm going to rebuild the database from scratch.