since new version autoupdate with snap package : no message can be send.
a part of the error message in the log section :
server.js:204 System âž” error Error sending message: Error: You are not authorized to change message properties at validateUserIdentity (app/lib/server/functions/sendMessage.js:164:9) at sendMessage (app/lib/server/functions/sendMessage.js:175:3) at executeSendMessage (app/lib/server/methods/sendMessage.js:76:10) at MethodInvocation.sendMessage (app/lib/server/methods/sendMessage.js:104:10) at maybeAuditArgumentChecks (packages/ddp-server/livedata_server.js:1771:12) at DDP._CurrentMethodInvocation.withValue (packages/ddp-server/livedata_server.js:719:19) at Meteor.EnvironmentVariable.EVp.withValue (packages/meteor.js:1234:12) at DDPServer._CurrentWriteFence.withValue (packages/ddp-server/livedata_server.js:717:46) at Meteor.EnvironmentVariable.EVp.withValue (packages/meteor.js:1234:12) at Promise (packages/ddp-server/livedata_server.js:715:46) at new Promise (
I have the same problem.
Rocket.Chat SNAP. Version 2.4.2. App engine version 1.11.0. Debian 10.
The rocketchat-server.rocketchat-caddy is always inactive (but enable).
even after restart it by the command: snap start rocketchat-server.rocketchat-caddy
Temporary workaround below
In the admin message settings (/admin/Message).
Turn off "Set a User Name to Alias in Message"

@lewisf2001uk thank you!
See #16097
Hi.
After we made an upgrade from 2.3.X to 2.4.0 we do have the same error, whenever trying to add new poll. On client there is feedback: "An error occured when trying to send the gif " and in logs:
I20200122-14:43:18.881(1) server.js:204 System âž” error Error sending message:
Error: You are not authorized to change message properties
at validateUserIdentity (app/lib/server/functions/sendMessage.js:164:9)
at sendMessage (app/lib/server/functions/sendMessage.js:174:2)
at MethodInvocation.sendMessage (app/lib/server/methods/sendMessage.js:86:11)
at MethodInvocation.methodsMap.(anonymous function) (app/lib/server/lib/debug.js:67:34)
at maybeAuditArgumentChecks (packages/ddp-server/livedata_server.js:1771:12)
at DDP._CurrentMethodInvocation.withValue (packages/ddp-server/livedata_server.js:1689:15)
at Meteor.EnvironmentVariable.EVp.withValue (packages/meteor.js:1234:12)
at resolve (packages/ddp-server/livedata_server.js:1687:36)
at new Promise (
at Server.applyAsync (packages/ddp-server/livedata_server.js:1686:12)
at Server.apply (packages/ddp-server/livedata_server.js:1625:26)
at Server.call (packages/ddp-server/livedata_server.js:1607:17)
at DDPCommon.MethodInvocation.Meteor.runAsUser (app/apps/server/bridges/messages.js:19:17)
at packages/dispatch_run-as-user.js:211:14
at Meteor.EnvironmentVariable.EVp.withValue (packages/meteor.js:1234:12)
at Object.Meteor.runAsUser (packages/dispatch_run-as-user.js:210:33)
at Promise.asyncApply (app/apps/server/bridges/messages.js:18:10)
at /opt/Rocket.Chat/programs/server/npm/node_modules/meteor/promise/node_modules/meteor-promise/fiber_pool.js:43:40
Do you have any propositions or should we create completly new incident?
forgot to mention, that proposed parameter is disabled in our case. OS: Centos 7.7.
I'm quite sure your problem is because we changed how the alias usage works, now only bot role can set the alias...
closing as duplicate of https://github.com/RocketChat/Rocket.Chat/issues/16097
Most helpful comment
Temporary workaround below

In the admin message settings (/admin/Message).
Turn off "Set a User Name to Alias in Message"