First of all, make sure that Acronis True Image 2019 detects your new SSD both in Windows and under the Acronis rescue media. If there is a problem, see What to do if Acronis True Image 2019 does not recognize your SSD.
SSD size
As SSDs usually have less capacity than HDDs, the occupied space on your old hard disk may exceed the size of your SSD. If this is the case, migration is not possible.
To reduce amount of data on your system disk, try the following:
Note that for stable operation, Windows needs to have several GB of free space on the system partition.
Which migration method to choose
If your system disk consists of a single partition (not counting the hidden System Reserved partition), you can try to migrate to the SSD using the Clone tool. For more information see Cloning a hard disk.
However, we recommend to use the backup and recovery method in most cases. This method provides more flexibility and control over migration. See Migrating to an SSD using the backup and recovery method.