You are not alone, I am another victim with more than 190,000 siacoins stuck. Block explore clearly shows my deposit has been done but 0 credit in my account.
http://explore.sia.tech/hashes/95437558571b645df4d2b23876bdd1032b34545dc1368ea1f89fa14dbdb76e5cSiacoin Transaction Summary
SUMMARY OF TRANSACTION ID
Height 138643
Confirmations 34
Output Reference(s)
e72901972e8f51863fd147f4d73d5111cf9fa5a8d3941ad2c28300f5d4ca0451
Transaction Value 192,367.18 SC
Clearly a Ponzi scheme, they are using my coins to fulfill others' withdrawals. When I need to withdraw, they will need to wait for others' deposits.
I reckon same bad thing is happening on you.
Are you American citizen btw?