Since you are upgrading from 5.18.0 to the latest version, let us take a look at the SQL query that you need to run:
ALTER TABLE Reactions DROP PRIMARY KEY, ADD PRIMARY KEY (PostId, UserId, EmojiName);
Once that is completed, can you please confirm that the Reactions table look like this?
mysql> DESCRIBE Reactions;
+-----------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-----------+-------------+------+-----+---------+-------+
| UserId | varchar(26) | NO | PRI | NULL | |
| PostId | varchar(26) | NO | PRI | NULL | |
| EmojiName | varchar(64) | NO | PRI | NULL | |
| CreateAt | bigint(20) | YES | | NULL | |
+-----------+-------------+------+-----+---------+-------+
4 rows in set (0.00 sec)
Can you also set the FileLevel parameter to DEBUG as well so we can get more details on the error that you are seeing when attempt to bring up the server again?