My Philips BT-ALU ballast can light a 13W PLC tube, 18W T8 tube, 21W T5 tube, 22W curcle tube and 24W H tube respectively. But no matter what tube, if I change it to two, it will not light up. I don't know why

Are you trying to run 2 tubes in series off your choke ballast?

It is clearly written on the ballast, which can light up two tubes at the same time.

This ballast should be able to light up a pair of 2 F18T8 tubes and also a pair of 22w circlines in series because both of those lamps have an arc voltage drop of about 57v, but a 24w PL-L has an arc voltage drop of about 91v, which makes it incompatible in a 2 lamp series preheat circuit if the ballast is a 220v series choke. In addition, a pair F21T5 HE fluorescent tubes cannot run in series off a 220v choke because they each have an arc voltage drop of about 130v and a pair of 13w PL-C lamps cannot operate in series off a 220v choke because they also have an arc voltage drop of about 100v.

So I can't use the drag-and-drop function now because all my F36T8 tubes are in my hometown, and my father didn't allow me to buy tubes longer than 40 cm two years ago.And my TL5C/40W tube has already EOL

When ssesing tge ballast, the primary parameters to sucessfuly run a lamp are the lamp operating current (does it match the lamp rating when operating with tgat lamp?) and the ballast OCV (open circuit voltage; is it able to start and maintain the discharge?)
The power rating figure is not directly relevant, although it is indirectly linked with the voltages and currents.
In your case you tried to run two lamps where each requires about 260V OCV (so 520V in total) on a ballast with just 230V OCV. There is jzst not enough voltage room for the tubes to run.

And evenwhen youwould manage to ignite themsomehow, the F40 ballast feeds about 0.35..0.43A, which is double what the 21WT5 are designed for, so the lamp would blow.

And if you got an idea of operating the kamps in parallel, drop that idea, it won't work, only one lamp will light and take the whole current.
The discharge itself exhibits lower voltage drop when the current gets increased. So any imbalance between those two lamps and one will take the whole current (and blow up due to overload) and the other will just stay dark, with no current at all. So parallel connection you may use only when you want an instant backup lamp for the case one fails (then the second will take over), but always just one of them will light. This is used by some makers to achieve high reliability with HPS lamps: They put two parallel connected arctubes into one single lamp assembly. Of course each of those arctubes is designed to match the overall lamp electrical rating

Series twin circuits need special series twin starter switches also, they won’t light with standard 155/500 and FSU starters in, they need 155/200s or FS2s