what a svg size of your aprite? if sprite resolution is more than 480*360 then he can changes size to only lower then 100 % size.
to solve this create:
empty costume - you can resize sprite with this costume to 200-infinity%
64*64 costume - you can resize sprite with this costume to 50-300%
480*360 costume - you can resize sprite with this costume to 5-98%
1920*1080 costume - you can resize sprite with this costume to 0-30%
in turbowarp you can disable this forbiddens but in scratch you need to use this

when green flag clicked
switch costume to [ small costume]
set size to (200) %
switch costume to [ your costume]

or this

when green flag clicked
switch costume to [ big costume]
set size to (20) %
switch costume to [ your costume]